D3 callback when all transitions are done

endall.js

function endAll(transition, callback) {
  var n = 0
  transition.each(() => ++n)
    .each('end', () => (!--n && callback.apply(this, arguments)))
}

// Usage
// d3.selectAll('g').transition().call(endAll, allDone)

Seems to be built in now, with Promises.

https://github.com/d3/d3-transition#transition_end

Looks like we can do something like this:

d3.selectAll("g")
  .transition("name")
  .duration(1000)
  .end()
  .then(() => {
    // do something
  });

@phocks you literally saved my life