Use Lodash endsWith equivalent

[aduth]

Related: https://github.com/WordPress/gutenberg/pull/1674/files#r130091486
Related: #746

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/endsWith#Browser_compatibility

We do not use babel-polyfill or the like to polyfill ES2015+ base type prototype methods (e.g. Array#includes, String#endsWith), so we must be careful to use Lodash alternatives instead.

I'm not opposed to using a polyfill, though it introduces non-trivial bulk to the bundle size. This situation will improve in babel-preset-env@2.x (current alpha.16) with automatic feature detection.

https://github.com/babel/babel-preset-env/tree/2.0#usebuiltins-usage

Testing instructions:

Repeat testing instructions from #1674

[nylen]

Can we make use of this and other problematic methods a lint error?

[aduth]

Can we make use of this and other problematic methods a lint error?

We can match the identifier, but it's hard to know the type, so it's possible to hit false positives with custom classes containing endsWith on their prototype, or the endsWith Lodash method itself.

Here was Calypso's take on the problem: Automattic/wp-calypso#6117

Honestly, if we expect to use polyfilling eventually anyways, I'm not inclined to spend much effort on it.

[mtias]

Looks good.

[ellatrix]

Thanks Andrew! I should've checked.