Use the has API

[jeffrose]

Use the has API instead of stringifySupported and parseSupported in order to take advantage of has-aware AMD optimizers, like r.js and dojo.

function has( id ){
    if( id === 'json' ){
        return !!JSON;
    } else if( id === 'json-stringify' ){
        return typeof JSON.stringify === "function";
    } else if( id === 'json-parse' ){
        return typeof JSON.parse === "function";
    } else {
        return false;
    }
}

if( has( 'json-stringify' ) ){
...
}

if( has( 'json-parse' ) ){
...
}

[ghost]

Thanks for the report!

The problem with the suggested implementation is that it's not strictly equivalent to stringifySupported and parseSupported. has tests for existence, whereas JSON 3 performs feature tests to determine if the (possibly native) implementation is incorrect or incomplete. These bugs aren't restricted to older environments; browsers as recent as Safari 5.1 and IE 10 fail the tests. The tests are also important for detecting buggy libraries and polyfills (e.g., Prototype <= 1.6.1, JSON 2).

I can contribute JSON 3's feature tests to the has.js project (I presume that's what has-aware optimizers like Dojo use?)...but then devs will need to upgrade to the latest version of has.js for consistent behavior. If possible, I'd like to avoid tying JSON 3 to a particular version of another project.

I'm not familiar with how Dojo's optimizer works, so please forgive me if I'm misunderstanding the thrust of the issue.

[jeffrose]

Actually while has.js and dojo introduced the has API, from an optimizer perspective any library can implement it. For example poly.js uses it and Modernizr has an issue open to make use of it as well.

It is possible to configure the r.js and dojo optimizers to build for browsers with particular features. So instead of having a run-time decision, you can make the decision at build-time. For example...

// build.js
( {
    baseUrl: '.',
    ...
    has: {
        // Build for browsers that have valid JSON implementations
        'json-parse': true,
        'json-stringify': true,
        'json': true
    }
} )

... So code written like this...

...
if( has( 'json-parse' ) ){
    // Use native JSON.parse
} else {
    // Use polyfill
}
...

... becomes...

...
    // Use native JSON.parse
...

[ghost]

Ah, I see. Thanks very much for clarifying!

Does c54a4d7 look solid to you?

[jeffrose]

Looks good to me.