4. Target the latest standardized JavaScript version

4.1. Status

Accepted

4.2. Context

The Open edX community must write JavaScript in a way that ensures future support and the availability of modern features.

4.3. Decision

The Open edX community must write JavaScript consistent with the latest ECMA-262 specification in order to ensure future support, the largest community, and the availability of modern features.

4.4. Consequence

Not all browsers support the latest JavaScript features and syntax. To support this syntax in older browsers, the Open edX community must use Babel.

4.5. Rejected Alternatives

4.5.1. CoffeeScript

The Open edX codebase made heavy use of CoffeeScript for several years, but its use at edX has now been officially deprecated. Most of the language benefits of CoffeeScript were made available in JavaScript as of the ES2015 spec, and CoffeeScript’s community has largely moved on.

4.5.2. TypeScript

Several variants of typed JavaScript have grown in community popularity recently, with TypeScript as the most popular. The Open edX community believes adding typing to our JavaScript would raise the barrier to entry for less experienced front end developers, and that using TypeScript in particular would lock us into a tool with an uncertain future (as we experienced with CoffeeScript). If typing is an absolute necessity for a feature (e.g., an API client or sensitive business logic), Flow is recommended, as it can be incrementally added and evaluated alongside non-typed code.