[limsup]

Can someone explain what the "spread operator" is and how to use it?

[heydenberk]

Spread is like python's *args.

Instead of this:

  var mapArgs = function() {
    var args = Array.prototype.slice.call(arguments, 0, arguments.length - 1);
    var mapper = Array.prototype.slice.call(arguments, arguments.length - 1);
    return args.map(mapper);
  };

You can do this:

  var mapArgs = function(...args, mapper) {
    return args.map(mapper);
  };

And you can also use it to apply. Instead of:

  var max = Math.max.apply(null, [1, 2, 3, 4]);

You can do:

  var max = Math.max(...[1, 2, 3, 4]);

[jxm262]

heydenberk explained it well, but just to add some clarity on why you'd want to use prototype.apply for array as an argument -

http://stackoverflow.com/questions/2856059/passing-an-array-...

http://stackoverflow.com/questions/1316371/converting-a-java...

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

I'm still learning more about JS and so I'm no expert, but it seems to be similar in concept to use the ... in other languages. I think Groovy has something similar and Java has the varargs. They have obvious differences, but conceptually I think of it as passing in a variable number of args.

[jbaudanza]

https://gist.github.com/sebmarkbage/07bbe37bc42b6d4aef81

[claar]

Wow, the example in that gist:

  var component = <Component {...props} foo={'override'} />;

Wha?? For me, there's a point in a language where the benefits of syntactic sugar are outweighed by readability concerns.