In the specific D3 examples above, the advantages of ES6 have long been available in CoffeeScript.

Several ES6 features very much resemble the few ways coffeescript syntax differs from older versions of ecmascript. Arrow functions, destructured assignment, string templates.

In context, we were commenting on this:

    .attr('transform', d => `translate(${d.x + 1} 0)`)

which looks pretty similar to the coffeescript counterpart:

    .attr 'transform', (d) -> "translate(#{d.x + 1} 0)"

Five subtle differences, but it shows how the things that are new/different about ES6 are more similar to typescript and coffeescript than ES5.