setInterval with（this）

Question

Please, someone can explain me what is the meaning of (this) at the end of the function in a setInterval :

function Klass(name) {
      this.name = name;
      this.handle = null;

      this.startTimer = function() {

        this.handle = setInterval(function(obj) {

          return(function() {
            alert(obj.name);
            });

          }(this), 5000); // <-------------------- (this)

      }

Answer 1

The use of this in the construct is intended to preserve the meaning of this at the point setInterval is called for the actual call back that is executed at the given interval. Without the manual preservation this would become the owner of the function at the point setInterval was called.

Here's a very nice article on this subject

• http://www.quirksmode.org/js/this.html

Another way this could be done which may be a bit clearer is the following

var self = this
this.handle = setInterval(function() { alert(self.Name); }, 5000);