this

A JavaScript keyword that evaluates to different values in different execution contexts.

• Global and global functions
  • In strict mode, this === undefined
  • In sloppy mode, this === window

• Inside methods (even if the function was added to the object later)

  • Equal to object the method was called on, e.g.:

    var jake = {
      name: "Jake",
      greet: function(){
        console.log("Hi, my name is " + this.name);
      }
    }
    
    jake.greet() // this === jake
    var vagabondGreet = jake.greet;
    vagabondGreet(); // this === undefined (in strict mode)
    

• jQuery
  • In event handlers, this === event.target. E.g.

    $('button').on('click', function(event) {
    // this === event.target
    // $(this) === jQuery wrapped element, allowing jQuery methods
    $(this).css({backgroundColor: 'green'});
    });