An alternative to TypeScript is to use the BabelJS compiler. This is an open source project ECMAScript-2015 and beyond to the equivalent ECMAScript 5 JavaScript. A lot of the changes put in place for ECMAScript-2015 are syntactic niceties, so they can actually be represented in ECMAScript 5 JavaScript, although not as succinctly or as pleasantly. We've seen that already using class-like structures in ES 5. BabelJS is written in JavaScript, which means that the compilation from ECMAScript-2015 to ES 5 is possible directly on a web page. Of course, as seems to be the trend with compilers, the source code for BabelJS makes use of ES 6 constructs, so BabelJS must be used to compile BabelJS.

At the time of writing, the list of ES6 functions ...

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