How to pass “this” to window setInterval

Question

Suppose I have a function a:

function a() {
    this.b = 1;
    this.set = setInterval(function() {console.log(this.b);}, 200);
}

So when

Answer 1

Store a reference to this:

function a() {
    var self = this;
    self.b = 1;
    self.set = setInterval(function() {console.log(self.b);}, 200);
}

The anonymous function that you pass to setInterval has access to any variables in its containing scope, i.e., any local variables of function a(). The magic of JS closures keeps these variables alive even after a() has completed, and each invocation of a() gets its own closure.