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Allow duplicate keys in FormData

Summary: Right now `FormData` doesn't allow duplicate keys and uses the last value set for a duplicate key. I tested this in Chrome:
var formData = new FormData();
formData.append('key', 'value1');
formData.append('key', 'value2');

var request = new XMLHttpRequest();"POST", serverUrl);
and the request has both 'value1' and 'value2'.

I removed the duplicate key check in `FormData`. If people want to build appending or disallow duplicate keys, they can build either on top of this.
Closes #3556

Reviewed By: svcscm

Differential Revision: D2566999

Pulled By: nicklockwood

fb-gh-sync-id: 580e52e69376ebe9693e39a386cc540802b6d94f
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jesseruder authored and facebook-github-bot-5 committed Oct 21, 2015
1 parent 666833d commit 56fef9b6225ffc1ba87f784660eebe842866c57d
Showing with 6 additions and 14 deletions.
  1. +6 −14 Libraries/Network/FormData.js
@@ -47,26 +47,18 @@ type FormDataPart = {
class FormData {
_parts: Array<FormDataNameValuePair>;
_partsByKey: {[key: string]: FormDataNameValuePair};
constructor() {
this._parts = [];
this._partsByKey = {};
append(key: string, value: FormDataValue) {
var parts = this._partsByKey[key];
if (parts) {
// It's a bit unclear what the behaviour should be in this case.
// The XMLHttpRequest spec doesn't specify it, while MDN says that
// the any new values should appended to existing values. We're not
// doing that for now -- it's tedious and doesn't seem worth the effort.
parts[1] = value;
parts = [key, value];
this._partsByKey[key] = parts;
// The XMLHttpRequest spec doesn't specify if duplicate keys are allowed.
// MDN says that any new values should be appended to existing values.
// In any case, major browsers allow duplicate keys, so that's what we'll do
// too. They'll simply get appended as additional form data parts in the
// request body, leaving the server to deal with them.
this._parts.push([key, value]);
getParts(): Array<FormDataPart> {

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