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<!DOCTYPE html>
<html>
<head>
<title>
Payment Request API
</title>
<meta charset='utf-8'>
<script src='https://www.w3.org/Tools/respec/respec-w3c-common' class=
'remove'></script>
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name: "Adrian Bateman",
company: "Microsoft Corporation",
w3cid: 42763,
}, {
name: "Zach Koch",
company: "Google",
w3cid: 76588,
}, {
name: "Roy McElmurry",
company: "Facebook",
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previousMaturity: "WD",
previousPublishDate: "2016-07-05",
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</head>
<body>
<h1 id="title">
Payment Request API
</h1>
<section id='abstract'>
<p>
This specification standardizes an API to allow merchants (i.e. web
sites selling physical or digital goods) to utilize one or more payment
methods with minimal integration. User agents (e.g., browsers)
facilitate the payment flow between merchant and user.
</p>
</section>
<section id='sotd'>
<p>
The working group maintains <a href=
"https://github.com/w3c/payment-request/issues?utf8=%E2%9C%93&q=is%3Aopen%20is%3Aissue%20-label%3A%22Priority%3A%20Postponed%22%20">
a list of all bug reports that the group has not yet addressed</a>.
Pull requests with proposed specification text for outstanding issues
are strongly encouraged.
</p>
<p>
The deadline for comments for Candidate Recommendation is 31 October
2017.
</p>
<div class="note" title="Sending comments on this document">
<p>
If you wish to make comments regarding this document, please raise
them as <a href=
"https://github.com/w3c/payment-request/issues">GitHub issues</a>.
Only send comments by email if you are unable to raise issues on
GitHub (see links below). All comments are welcome.
</p>
</div>
<p>
The working group will demonstrate implementation experience by
producing an <a href=
"https://w3c.github.io/payment-request/reports/implementation.html">implementation
report</a>. The report will show two or more independent
implementations passing each mandatory test in the <a href=
"https://w3c-test.org/payment-request/">test suite</a> (i.e., each test
corresponds to a MUST requirement of the specification).
</p>
<p>
There has been no change in dependencies on other workings groups
during the development of this specification.
</p>
<section id="at-risk">
<h2>
Features at risk
</h2>
<p>
As this specification enters the Candidate Recommendation phase of
the W3C standardization process, the working group has identified the
following feature(s) as being "<dfn>at risk</dfn>" of being removed
from the specification. The working group seeks input from
implementers, developers, and the general public on whether these
features should remain in the specification. If no compelling use
cases are received, or if there is limited interest from
implementers, these features will be removed from the specification
before proceeding along the W3C Recommendation track.
</p>
<ul>
<li data-link-for="PaymentItem">
<a>PaymentItem</a>'s <a>type</a> member and the
<a>PaymentItemType</a> enum (see <a href=
"https://github.com/w3c/payment-request/issues/163">issue 163</a>).
</li>
<li data-link-for="PaymentRequest">As the <code>optional
detailsPromise</code> argument of the <a>show()</a> method was added
late in the Candidate Recommendation phase, the working group is
treating it "at risk" and considering moving it to a future version
of the specification. This is to avoid this version of the
specification from being delayed from progressing along the
Recommendation Track, in case we can't get two interoperable
implementations in a timely manner. However, if it gets interoperably
implemented relatively quickly, the feature will remain in this
version of the specification.
</li>
</ul>
</section>
</section>
<section class='informative'>
<h2>
Introduction
</h2>
<p>
This specification describes an API that allows <a>user agents</a>
(e.g., browsers) to act as an intermediary between three parties in a
transaction:
</p>
<ul>
<li>the payee: the merchant that runs an online store, or other party
that requests to be paid.
</li>
<li>the payer: the party that makes a purchase at that online store,
and who authenticates and authorizes payment as required.
</li>
<li>the <dfn data-lt="payment methods">payment method</dfn> provider:
the party that provides the means (e.g., credit card) that the payer
uses to pay, and that is accepted by the payee.
</li>
</ul>
<p>
The details of how to fulfill a payment request for a given <a>payment
method</a> is an implementation detail of a <dfn data-lt=
"payment handlers">payment handler</dfn>. Concretely, each payment
handler defines:
</p>
<dl>
<dt>
A <dfn>can make payment</dfn> algorithm:
</dt>
<dd>
How a payment handler determines whether it, or the user, can
potentially "make a payment" is also an implementation detail of a
payment handler. For an example, see the <a data-cite=
"payment-method-basic-card#can-makepayment">can make payment</a>
algorithm of [[payment-method-basic-card]].
</dd>
<dt>
<dfn>Steps to respond to a payment request</dfn>:
</dt>
<dd>
An algorithm that returns an object or <a data-cite=
"!WEBIDL#idl-dictionary">dictionary</a> that a merchant uses to
process or validate the transaction. The structure of this object is
specific to each <a>payment method</a>. For an example of such an
object, see the <code><a data-cite=
"payment-method-basic-card#dom-basiccardresponse">BasicCardResponse</a></code>
dictionary of [[payment-method-basic-card]].
</dd>
</dl>
<p>
This API also enables web sites to take advantage of more secure
payment schemes (e.g., tokenization and system-level authentication)
that are not possible with standard JavaScript libraries. This has the
potential to reduce liability for the merchant and helps protect
sensitive user information.
</p>
<section id="goals">
<h2>
Goals
</h2>
<ul>
<li>Allow the user agent to act as intermediary between merchants,
users, and <a>payment method</a> providers.
</li>
<li>Enable user agents to streamline the user's payment experience by
taking into account user preferences, merchant information, security
considerations, and other factors.
</li>
<li>Standardize (to the extent that it makes sense) the communication
flow between a merchant, user agent, and <a>payment method</a>
provider.
</li>
<li>Enable <a>payment method</a> providers to bring more secure
payment transactions to the web.
</li>
</ul>
<section id="out-of-scope">
<h2>
Out of scope
</h2>
<ul>
<li>Create a new <a>payment method</a>
</li>
<li>Integrate directly with payment processors
</li>
</ul>
</section>
</section>
</section>
<section class="informative">
<h2>
Examples of usage
</h2>
<p>
In order to use the API, the developer needs to provide and keep track
of a number of key pieces of information. These bits of information are
passed to the <a>PaymentRequest</a> constructor as arguments, and
subsequently used to update the payment request being displayed to the
user. Namely, these bits of information are:
</p>
<ul>
<li>The <var>methodData</var>: A sequence of <a>PaymentMethodData</a>s
that represents the <a>payment methods</a> that the site supports
(e.g., "we support card-based payments, but only Visa and MasterCard
credit cards.").
</li>
<li>The <var>details</var>: The details of the transaction, as a
<a>PaymentDetailsInit</a> dictionary. This includes total cost, and
optionally a list of goods or services being purchased, for physical
goods, and shipping options. Additionally, it can optionally include
"modifiers" to how payments are made. For example, "if you pay with a
credit card of type X, it incurs a US$3.00 processing fee".
</li>
<li>The <var>options</var>: Optionally, a list of things as
<a>PaymentOptions</a> that the site needs to deliver the good or
service (e.g., for physical goods, the merchant will typically need an
physical address to ship to. For digital goods, an email will usually
suffice).
</li>
</ul>
<p data-link-for="PaymentRequest">
Once a <a>PaymentRequest</a> is constructed, it's presented to the end
user via the <a>show()</a> method. The <a>show()</a> returns a promise
that, once the user confirms request for payment, results in a
<a>PaymentResponse</a>.
</p>
<section>
<h3>
The <code>methodData</code> argument
</h3>
<p>
The <var>methodData</var> sequence contains <a>PaymentMethodData</a>
dictionaries containing the <a>payment method identifiers</a> for the
<a>payment methods</a> that the web site accepts and any associated
<a>payment method</a> specific data.
</p>
<pre class="example js" title="The `methodData` argument">
const methodData = [
{
supportedMethods: "basic-card",
data: {
supportedNetworks: ["visa", "mastercard"],
supportedTypes: ["debit", "credit"],
},
},
{
supportedMethods: "https://example.com/bobpay",
data: {
merchantIdentifier: "XXXX",
bobPaySpecificField: true,
},
},
];
</pre>
</section>
<section>
<h3>
The <code>details</code> argument
</h3>
<p>
The <var>details</var> contains information about the transaction
that the user is being asked to complete, such as the line items in
an order.
</p>
<pre class="example js" title="The `details` argument">
const details = {
id: "super-store-order-123-12312",
displayItems: [
{
label: "Sub-total",
amount: { currency: "USD", value: "55.00" },
},
{
label: "Sales Tax",
amount: { currency: "USD", value: "5.00" },
type: "tax"
},
],
total: {
label: "Total due",
// The total is USD$65.00 here because we need to
// add shipping (below). The selected shipping
// costs USD$5.00.
amount: { currency: "USD", value: "65.00" },
},
};
</pre>
<section>
<h4>
Shipping options
</h4>
<p>
Here we see an example of how to add two shipping options to the
<var>details</var>.
</p>
<pre class="example js" title="Adding shipping options">
const shippingOptions = [
{
id: "standard",
label: "🚛 Ground Shipping (2 days)",
amount: { currency: "USD", value: "5.00" },
selected: true,
},
{
id: "drone",
label: "🚀 Drone Express (2 hours)",
amount: { currency: "USD", value: "25.00" }
},
];
Object.assign(details, { shippingOptions });
</pre>
</section>
<section>
<h4>
Conditional modifications to payment request
</h4>
<p>
Here we see how to add a processing fee for using a credit card.
Notice that it requires recalculating the total.
</p>
<pre class="example js" title=
"Modifying payment request based on card type">
// Credit card incurs a $3.00 processing fee.
const creditCardFee = {
label: "Credit card processing fee",
amount: { currency: "USD", value: "3.00" },
};
// Modifiers apply when the user chooses to pay with
// a credit card.
const modifiers = [
{
additionalDisplayItems: [creditCardFee],
supportedMethods: "basic-card",
total: {
label: "Total due",
amount: { currency: "USD", value: "68.00" },
},
data: {
supportedTypes: "credit",
},
},
];
Object.assign(details, { modifiers });
</pre>
</section>
</section>
<section>
<h3>
The <code>options</code> argument
</h3>
<p>
The <var>options</var> dictionary contains information the developer
needs from the user to perform the payment (e.g., the payer's name
and shipping address).
</p>
<pre class="example" title="The `options` argument">
const options = {
requestPayerEmail: false,
requestPayerName: true,
requestPayerPhone: false,
requestShipping: true,
}
</pre>
</section>
<section>
<h3>
Constructing a <code>PaymentRequest</code>
</h3>
<p>
Having gathered all the prerequisite bits of information, we can now
construct a <a>PaymentRequest</a> and request that the browser
present it to the user:
</p>
<pre class="example" title="Constructing a `PaymentRequest`">
async function doPaymentRequest() {
try {
const request = new PaymentRequest(methodData, details, options);
// See below for a detailed example of handling these events
request.onshippingaddresschange = ev => ev.updateWith(details);
request.onshippingoptionchange = ev => ev.updateWith(details);
const response = await request.show();
await validateResponse(response);
} catch (err) {
// AbortError, SecurityError
console.error(err);
}
}
async function validateResponse(response) {
try {
if (await checkAllValuesAreGood(response)) {
await response.complete("success");
} else {
await response.complete("fail");
}
} catch (err) {
// Something went wrong...
await response.complete("fail");
}
}
doPaymentRequest();
</pre>
</section>
<section>
<h3>
Handling events and updating the payment request
</h3>
<p>
Prior to the user accepting to make payment, the site is given an
opportunity to update the payment request in response to user input.
This can include, for example, providing additional shipping options
(or modifying their cost), removing items that cannot ship to a
particular address, etc.
</p>
<pre class="example" title="Registering event handlers">
const request = new PaymentRequest(methodData, details, options);
// Async update to details
request.onshippingaddresschange = ev => {
ev.updateWith(checkShipping(request));
};
// Sync update to the total
request.onshippingoptionchange = ev => {
const shippingOption = shippingOptions.find(
option => option.id === request.id
);
const newTotal = {
currency: "USD",
label: "Total due",
value: calculateNewTotal(shippingOption),
};
ev.updateWith({ ...details, total: newTotal });
};
async function checkShipping(request) {
try {
const json = request.shippingAddress.toJSON();
await ensureCanShipTo(json);
const { shippingOptions, total } = await calculateShipping(json);
return { ...details, shippingOptions, total };
} catch (err) {
return { ...details, error: `Sorry! we can't ship to your address.` };
}
}
</pre>
</section>
<section data-link-for="PaymentResponse">
<h3>
POSTing payment response back to a server
</h3>
<p>
It's expected that data in a <a>PaymentResponse</a> will be POSTed
back to a server for processing. To make this as easy as possible,
<a>PaymentResponse</a> provides a <a>toJSON()</a> method that
serializes the object directly into JSON. This makes it trivial to
POST the resulting JSON back to a server using the <a data-cite=
"fetch">Fetch API</a>:
</p>
<pre class="example" title="POSTing with `fetch()`">
async function doPaymentRequest() {
const payRequest = new PaymentRequest(methodData, details, options);
const payResponse = await payRequest.show();
let result = "";
try {
const httpResponse = await fetch("/process-payment", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: payResponse.toJSON(),
});
result = httpResponse.ok ? "success" : "fail";
} catch (err) {
console.error(err);
result = "fail";
}
await payResponse.complete(result);
}
doPaymentRequest();
</pre>
</section>
</section>
<section data-dfn-for="PaymentRequest" data-link-for="PaymentRequest">
<h2>
<dfn>PaymentRequest</dfn> interface
</h2>
<pre class="idl">
[Constructor(sequence<PaymentMethodData> methodData, PaymentDetailsInit details, optional PaymentOptions options),
SecureContext, Exposed=Window]
interface PaymentRequest : EventTarget {
Promise<PaymentResponse> show(optional Promise<PaymentDetailsUpdate> detailsPromise);
Promise<void> abort();
Promise<boolean> canMakePayment();
readonly attribute DOMString id;
readonly attribute PaymentAddress? shippingAddress;
readonly attribute DOMString? shippingOption;
readonly attribute PaymentShippingType? shippingType;
attribute EventHandler onshippingaddresschange;
attribute EventHandler onshippingoptionchange;
};
</pre>
<div class="note">
<p>
A developer creates a <a>PaymentRequest</a> to make a payment
request. This is typically associated with the user initiating a
payment process (e.g., by activating a "Buy," "Purchase," or
"Checkout" button on a web site, selecting a "Power Up" in an
interactive game, or paying at a kiosk in a parking structure). The
<a>PaymentRequest</a> allows developers to exchange information with
the <a>user agent</a> while the user is providing input (up to the
point of user approval or denial of the payment request).
</p>
<p data-link-for="PaymentRequest">
The <a>shippingAddress</a>, <a>shippingOption</a>, and
<a>shippingType</a> attributes are populated during processing if the
<a data-lt="PaymentOptions.requestShipping">requestShipping</a>
member is set.
</p>
</div>
<p data-link-for="PaymentRequest">
Because the simultaneous display of multiple <a>PaymentRequest</a> user
interfaces might confuse the user, this specification limits the
<a>user agent</a> to displaying one at a time via the <a>show()</a>
method. This is ensured by a <dfn>payment request is showing</dfn>
boolean.
</p>
<section>
<h2>
Constructor
</h2>
<p>
The <a>PaymentRequest</a> is constructed using the supplied
<var>methodData</var> list including any <a>payment method</a>
specific <a data-lt="PaymentMethodData.data">data</a>, the payment
<var>details</var>, and the payment <var>options</var>.
</p>
<p data-tests="payment-request-constructor.https.html">
The <code><dfn data-lt=
"PaymentRequest.PaymentRequest()">PaymentRequest(<var>methodData</var>,
<var>details</var>, <var>options</var>)</dfn></code> constructor MUST
act as follows:
</p>
<ol data-link-for="PaymentDetailsBase" class="algorithm">
<li data-tests=
"active-document-cross-origin.https.sub.html, active-document-same-origin.https.html, removing-allowpaymentrequest.https.sub.html, setting-allowpaymentrequest-timing.https.sub.html, setting-allowpaymentrequest.https.sub.html">
If the <a>current settings object</a>'s <a data-cite=
"!HTML#responsible-document">responsible document</a> is not
<a>allowed to use</a> the feature indicated by attribute name
<a>allowpaymentrequest</a>, then <a>throw</a> a
"<a>SecurityError</a>" <a>DOMException</a>.
</li>
<li>Let <var>serializedMethodData</var> be an empty list.
</li>
<li>Establish the request's id:
<ol>
<li data-tests="payment-request-id-attribute.https.html">If <var>
details</var>.<a data-lt="PaymentDetailsInit.id">id</a> is
missing, add an <a data-lt="PaymentDetailsInit.id">id</a>
member to <var>details</var> and set its value to a
<abbr title="Universally Unique Identifier">UUID</abbr>
[[!RFC4122]].
</li>
</ol>
</li>
<li>Process payment methods:
<ol data-link-for="PaymentMethodData">
<li>If the length of the <var>methodData</var> sequence is zero,
then <a>throw</a> a <a>TypeError</a>, optionally informing the
developer that at least one <a>payment method</a> is required.
</li>
<li>For each <var>paymentMethod</var> of <var>methodData</var>:
<ol>
<li data-tests=
"payment-request-ctor-pmi-handling.https.html">Run the steps
to <a data-cite=
"payment-method-id#dfn-validate-a-payment-method-identifier">
validate a payment method identifier</a> with
<var>paymentMethod</var>.<a data-lt=
"PaymentMethodData.supportedMethods">supportedMethods</a>.
If it returns false, then throw a <a>RangeError</a>
exception and terminate this algorithm. Optionally, inform
the developer that the payment method identifier is
invalid.
</li>
<li>If the <a data-lt="PaymentMethodData.data">data</a>
member of <var>paymentMethod</var> is missing, let
<var>serializedData</var> be null. Otherwise, let
<var>serializedData</var> be the result of
<a>JSON-serializing</a>
<var>paymentMethod</var>.<a data-lt="PaymentMethodData.data">data</a>
into a string. Rethrow any exceptions.
</li>
<li>Add the tuple (<var>paymentMethod</var>.<a data-lt=
"PaymentMethodData.supportedMethods">supportedMethods</a>,
<var>serializedData</var>) to
<var>serializedMethodData</var>.
</li>
</ol>
</li>
</ol>
</li>
<li data-link-for="PaymentDetailsInit">Process the total:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize total</a>
<var>details</var>.<a>total</a>.<a data-lt=
"PaymentItem.amount">amount</a>. Rethrow any exceptions.
</li>
</ol>
</li>
<li>If the <a>displayItems</a> member of <var>details</var> is
present, then for each <var>item</var> in
<var>details</var>.<a>displayItems</a>:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize amount</a>
<var>item</var>.<a data-lt="PaymentItem.amount">amount</a>.
Rethrow any exceptions.
</li>
</ol>
</li>
<li>Let <var>selectedShippingOption</var> be null.
</li>
<li>If the <a data-lt=
"PaymentOptions.requestShipping">requestShipping</a> member of <var>
options</var> is present and set to true, process shipping options:
<ol>
<li>Let <var>options</var> be an empty <code><a data-cite=
"!WEBIDL#idl-sequence">sequence</a></code><<a>PaymentShippingOption</a>>.
</li>
<li>If the <a>shippingOptions</a> member of <var>details</var> is
present, then:
<ol data-link-for="PaymentShippingOption">
<li>Let <var>seenIDs</var> be an empty list.
</li>
<li>Set <var>options</var> to
<var>details</var>.<a data-link-for=
"PaymentDetailsBase">shippingOptions</a>.
</li>
<li>For each <var>option</var> in <var>options</var>:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize amount</a>
<var>item</var>.<a data-lt=
"PaymentItem.amount">amount</a>. Rethrow any
exceptions.
</li>
<li>If <var>seenIDs</var> contains
<var>option</var>.<a>id</a>, then throw a
<a>TypeError</a>. Optionally, inform the developer that
shipping option IDs must be unique.
</li>
<li>Otherwise, append <var>option</var>.<a>id</a> to
<var>seenIDs</var>.
</li>
</ol>
</li>
<li>For each <var>option</var> in <var>options</var>:
<ol>
<li>If <var>option</var>.<a>selected</a> is true, then
set <var>selectedShippingOption</var> to
<var>option</var>.<a>id</a>.
</li>
</ol>
</li>
</ol>
</li>
<li>Set <var>details</var>.<a data-lt=
"PaymentDetailsBase.shippingOptions">shippingOptions</a> to <var>
options</var>.
</li>
</ol>
</li>
<li>Let <var>serializedModifierData</var> be an empty list.
</li>
<li data-link-for="PaymentDetailsBase">Process payment details
modifiers:
<ol>
<li>Let <var>modifiers</var> be an empty <code><a data-cite=
"!WEBIDL#idl-sequence">sequence</a></code><<a>PaymentDetailsModifier</a>>.
</li>
<li>If the <a>modifiers</a> member of <var>details</var> is
present, then:
<ol>
<li>Set <var>modifiers</var> to
<var>details</var>.<a>modifiers</a>.
</li>
<li>For each <var>modifier</var> of <var>modifiers</var>:
<ol>
<li>If the <a data-lt=
"PaymentDetailsModifier.total">total</a> member of <var>
modifier</var> is present, then:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize total</a>
<var>modifier</var>.<a data-lt=
"PaymentDetailsModifier.total">total</a>.<a data-lt="PaymentItem.amount">amount</a>.
Rethrow any exceptions.
</li>
</ol>
</li>
<li>If the <a data-lt=
"PaymentDetailsModifier.additionalDisplayItems">additionalDisplayItems</a>
member of <var>modifier</var> is present, then for each
<var>item</var> of <var>modifier</var>.<a data-lt=
"PaymentDetailsModifier.additionalDisplayItems">additionalDisplayItems</a>:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize amount</a>
<var>item</var>.<a data-lt=
"PaymentItem.amount">amount</a>. Rethrow any
exceptions.
</li>
</ol>
</li>
<li>If the <a data-lt=
"PaymentDetailsModifier.data">data</a> member of
<var>modifier</var> is missing, let
<var>serializedData</var> be null. Otherwise, let
<var>serializedData</var> be the result of
<a>JSON-serializing</a> <var>modifier</var>.<a data-lt=
"PaymentDetailsModifier.data">data</a> into a string.
Rethrow any exceptions.
</li>
<li>Add <var>serializedData</var> to
<var>serializedModifierData</var>.
</li>
<li>Remove the <a data-lt="PaymentDetailsModifier.data">
data</a> member of <var>modifier</var>, if it is
present.
</li>
</ol>
</li>
</ol>
</li>
<li>Set <var>details</var>.<a data-lt=
"PaymentDetailsBase.modifiers">modifiers</a> to
<var>modifiers</var>.
</li>
</ol>
</li>
<li>Let <var>request</var> be a new <a>PaymentRequest</a>.
</li>
<li>Set <var>request</var>.<a>[[\options]]</a> to <var>options</var>.
</li>
<li>Set <var>request</var>.<a>[[\state]]</a> to "<a>created</a>".
</li>
<li>Set <var>request</var>.<a>[[\updating]]</a> to false.
</li>
<li>Set <var>request</var>.<a>[[\details]]</a> to <var>details</var>.
</li>
<li>Set <var>request</var>.<a>[[\serializedModifierData]]</a> to
<var>serializedModifierData</var>.
</li>
<li>Set <var>request</var>.<a>[[\serializedMethodData]]</a> to <var>
serializedMethodData</var>.
</li>
<li>Set the value of <var>request</var>'s <a data-lt=
"PaymentRequest.shippingOption">shippingOption</a> attribute to <var>
selectedShippingOption</var>.
</li>
<li>Set the value of the <a data-lt="PaymentRequest.shippingAddress">
shippingAddress</a> attribute on <var>request</var> to null.
</li>
<li>If <var>options</var>.<a data-lt=
"PaymentOptions.requestShipping">requestShipping</a> is set to true,
then set the value of the <a data-lt=
"PaymentRequest.shippingType">shippingType</a> attribute on
<var>request</var> to <var>options</var>.<a data-lt=
"PaymentOptions.shippingType">shippingType</a>. Otherwise, set it to
null.
</li>
<li>Return <var>request</var>.
</li>
</ol>
</section>
<section data-dfn-for="PaymentRequest" data-link-for="PaymentRequest">
<h2>
<dfn>id</dfn> attribute
</h2>
<p data-tests="payment-request-id-attribute.https.html">
When getting, the <a>id</a> attribute returns this
<a>PaymentRequest</a>'s <a>[[\details]]</a>.<a data-lt=
"PaymentDetailsInit.id">id</a>.
</p>
</section>
<section data-dfn-for="PaymentRequest" data-link-for="PaymentRequest">
<h2>
<dfn>show()</dfn> method
</h2>
<div class="note">
<p>
The <a>show()</a> method is called when a developer wants to begin
user interaction for the payment request. The <a>show()</a> method
returns a <a>Promise</a> that will be resolved when the <a>user
accepts the payment request</a>. Some kind of user interface will
be presented to the user to facilitate the payment request after
the <a>show()</a> method returns.
</p>
<p>
It is not possible to show multiple <a>PaymentRequest</a>s at the
same time within one <a>user agent</a>. If a <a>PaymentRequest</a>
is already showing, calling <a>show()</a> —from any Web site— will
return a promise rejected with an "<a>AbortError</a>"
<a>DOMException</a>.
</p>
</div>
<p data-tests=
"payment-request-show-method.https.html, payment-request-show-method-manual.https.html">
The <code><a data-lt="show()">show(detailsPromise)</a></code> method
MUST act as follows:
</p>
<ol class="algorithm">
<li data-tests=
"payment-request-show-method-manual.https.html, show-method-postmessage-manual.https.html">
If the method was not <a>triggered by user activation</a>, return a
promise rejected with a "<a>SecurityError</a>" <a>DOMException</a>
and terminate this algorithm.
</li>
<li>Let <var>request</var> be the <a>PaymentRequest</a> object on
which the method is called.
</li>
<li>Let <var>document</var> be <var>request</var>'s <a data-cite=
"!HTML#concept-relevant-global">relevant global object</a>'s
<a data-cite="!HTML#concept-document-window">associated Document</a>.
</li>
<li data-tests="rejects_if_not_active.https.html">If
<var>document</var> is not <a data-cite="!HTML#fully-active">fully
active</a>, then return a promise rejected with an
"<a>AbortError</a>" <a>DOMException</a>.
</li>
<li>
<p>
Optionally, if the <a>user agent</a> wishes to disallow the call
to <a>show()</a> to protect the user, then return a promise
rejected with a "<a>SecurityError</a>" <a>DOMException</a>. For
example, the <a>user agent</a> may limit the rate at which a page
can call <a>show()</a>, as described in the <a href=
"#privacy">privacy considerations</a> section.
</p>
</li>
<li>If <var>request</var>.<a>[[\state]]</a> is not "<a>created</a>"
then return a promise rejected with an "<a>InvalidStateError</a>" <a>
DOMException</a>.
</li>
<li>If the <a>user agent</a>'s <a>payment request is showing</a>
boolean is true, then return a promise rejected with an
"<a>AbortError</a>" <a>DOMException</a>.
</li>
<li>Set <var>request</var>.<a>[[\state]]</a> to "<a>interactive</a>".
</li>
<li>Let <var>acceptPromise</var> be a new <a>Promise</a>.
</li>
<li>Set <var>request</var>.<a>[[\acceptPromise]]</a> to
<var>acceptPromise</var>.
</li>
<li>
<p>
Optionally:
</p>
<ol>
<li>Reject <var>acceptPromise</var> with an "<a>AbortError</a>"
<a>DOMException</a>.
</li>
<li>Set <var>request</var>.<a>[[\state]]</a> to "<a>closed</a>".
</li>
<li>Return <var>acceptPromise</var>.
</li>
</ol>
<p class="note">
This allows the <a>user agent</a> to act as if the user had
immediately <a data-lt="user aborts the payment request">aborted
the payment request</a>, at its discretion. For example, in
"private browsing" modes or similar, user agents might take
advantage of this step.
</p>
</li>
<li>Set the <a>user agent</a>'s <a>payment request is showing</a>
boolean to true.
</li>
<li>Return <var>acceptPromise</var> and perform the remaining steps
<a>in parallel</a>.
</li>
<li>Let <var>handlers</var> be an empty <a>list</a>.
</li>
<li>For each <var>paymentMethod</var> tuple in
<var>request</var>.<a>[[\serializedMethodData]]</a>:
<ol>
<li>Let <var>identifier</var> be the first element in the
<var>paymentMethod</var> tuple.
</li>
<li>Let <var>data</var> be the result of <a data-cite=
"!ECMASCRIPT#sec-json.parse">JSON-parsing</a> the second element
in the <var>paymentMethod</var> tuple.
</li>
<li>If required by the specification that defines the
<var>identifer</var>, then <a data-cite=
"!WEBIDL#dfn-convert-ecmascript-to-idl-value">convert</a>
<var>data</var> to an IDL value. Otherwise, <a data-cite=
"!WEBIDL#dfn-convert-ecmascript-to-idl-value">convert</a> to
<a data-cite="!WEBIDL#idl-object">object</a>.
</li>
<li>If conversion results in an error, reject
<var>acceptPromise</var> with that error and terminate this
algorithm.
</li>
<li>Let <var>registeredHandlers</var> be a <a>list</a> of
registered payment handlers for the payment method
<var>identifier</var>.
</li>
<li>For each <var>handler</var> in <var>registeredHandlers</var>:
<ol>
<li>Let <var>canMakePayment</var> be the result of running
<var>handler</var>'s <a>can make payment</a> algorithm with
<var>data</var>.
</li>
<li>If <var>canMakePayment</var> is true, then append
<var>handler</var> to <var>handlers</var>.
</li>
</ol>
</li>
</ol>
</li>
<li>If <var>handlers</var> is empty, then reject
<var>acceptPromise</var> with a "<a>NotSupportedError</a>"
<a>DOMException</a>, and set the <a>user agent</a>'s <a>payment
request is showing</a> boolean to false.
</li>
<li>Otherwise, present a user interface that will allow the user to
interact with the <var>handlers</var>. The user agent SHOULD
prioritize the preference of the user when presenting payment
methods.
</li>
<li data-tests=
"show-method-optional-promise-rejects-manual.https.html, show-method-optional-promise-resolves-manual.https.html">
If <var>detailsPromise</var> was passed, then:
<ol>
<li>Set <var>request</var>.<a>[[\updating]]</a> to true.
</li>
<li>Disable the user interface user interface that will allow the
user to interact with the <var>handlers</var>
</li>
<li>Run the <a>update a <code>PaymentRequest</code>'s details
algorithm</a> with <var>detailsPromise</var> and
<var>request</var>.
</li>
<li>Wait for the <var>detailsPromise</var> to settle.
<p class="note">