JavaScript-apply-call-and-blind.md

JavaScript apply, call and blind

• They are all prototype methods of Function.prototype

Function.prototype.apply() Calls a function and sets its this to the provided value. accepts a single array of arguments

Function.prototype.bind() Creates a new function. The new function has its this set to the provided value with a given sequence of arguments provided when the new function was called

Function.prototype.call() Executes a function and sets its this to the provided value. Unlike apply(), it accepts an argument list

function.apply(thisArgs, [argsArray])

var numbers = [5, 6, 2, 3, 7];

var max = Math.max.apply(null, numbers);

console.log(max);
// expected output: 7

var min = Math.min.apply(null, numbers);

console.log(min);
// expected output: 2

Function.bind(thisArgs[, arg1[, arg2[, ...]]])

var module = {
  x: 42,
  getX: function() {
    return this.x;
  }
}

var unboundGetX = module.getX;
console.log(unboundGetX()); // The function gets invoked at the global scope
// expected output: undefined

var boundGetX = unboundGetX.bind(module);
console.log(boundGetX());
// expected output: 42

More on .apply():

• But beware: in using apply this way, you run the risk of exceeding the JavaScript engine's argument length limit. The consequences of applying a function with too many arguments (think more than tens of thousands of arguments) vary across engines (JavaScriptCore has hard-coded argument limit of 65536)
• If your value array might grow into the tens of thousands, use a hybrid strategy: apply your function to chunks of the array at a time.