README.md

is-es5-supported.js

does this JavaScript environment conform to ECMAScript 5?

What is this?

I made this after reading Kangax's terrific ES5 compatibility table. Rather than feature-detect every single piece of ECMAScript 5, I've selected the smallest number of tests to identify non-conformant JavaScript environments.

parseInt() ignores leading zeros

• after this test, we get a false in most old browsers

Strict Mode

• after this test, we get a false in Internet Explorer 9 and environments or apps that load ES5-shim

Date.prototype.toISOString

• after this test, we get a false in EJS

Job done!

Supported Environments

I've manually tested in a range of environments:

• true: Node.js (0.12), Chrome (43), Safari (8), Firefox (38), Internet Explorer (10, 11), Edge

• false: Internet Explorer (6, 7, 8, 9)

Usage

• CommonJS (e.g. Node.js, Browserify, etc) use index.js

var isES5Supported = require('is-es5-supported');
console.log(isES5Supported); // `true` or `false`

• dist/index.js is a UMD-wrapped version for browsers and AMD

<script src="dist/index.js"></script>
<script>
console.log(isES5Supported); // `true` or `false`
</script>

Known Issues

• this approach does assume correlations between the 3 included tests and the rest of the ECMASCript 5 implementation, which might not return correct results in exotic environments

• Internet Explorer 10 Platform Preview 2 will get a false (who cares?)