Function returning function for convenience. Also Function.prototype.apply(). Source: http://yehudakatz.com/2011/08/11/understanding-javascript-function-invocation-and-this/

func-apply

var bind = function(func, thisValue) {
  return function() {
    return func.apply(thisValue, arguments);
  }
}
 
var boundHello = bind(person.hello, person);
boundHello("world") // "Brendan Eich says hello world"