Difference between -> and => in CoffeeScript

Thin arrow functions, -> are used to describe functions.

    square = (x) -> x*x
    cube = (x) -> x*x*x
    pow = (num, power) -> num**power

Equivalent JS:

    var cube, pow, square;

    square = function(x) {
      return x * x;
    };

    cube = function(x) {
      return x * x * x;
    };

    pow = function(num, power) {
      return Math.pow(num, power);
    };

Fat arrow functions, => are used to describe functions that are immediately invoked with current scope.

    run = () ->
        this.names = ["sir", "boast", "a", "lot"];
        reproduce = () => 
            _this.names.forEach((x)->
                console.log(x)
            )
        reproduce

Output of which is:

    var run;

    run = function() {
      var reproduce;
      this.names = ["sir", "boast", "a", "lot"];
      reproduce = (function(_this) {
        return function() {
          return _this.names.forEach(function(x) {
            return console.log(x);
          });
        };
      })(this);
      return reproduce;
    };

    run()();

Basically, a = () -> 10 is var a = function(){ return 10; } and a = () => 10 is var a = (function(_this){ var a = function(){ return 10; } })(this);