I am confused about using apply or call method correctly. I know that apply is passing an array to the function and call is passing strings to a function. For example the code b
this
is the scope of the Apply/Call
function. An example is:
function test() {
alert(this.a);
}
(function () {
this.a = "test";
test();//test
var self = this;
(function () {
this.a = "Foo";
test();//Foo
test.apply(self, []);//test
}());
}());
The first argument will be the this
in your function.
ie:
var p = {"name":"someone"};
function myFunction(a, b) {
console.log(this);
return a*b;
}
var myArray = [10,2];
myFunction.apply(p, myArray); //log output shows {"name":"someone"}
It's the context for the function. If you have this.something inside the function, it will access that particular property from that context object.
function foo(bar) {
this.bar = bar;
}
foo.apply(this, ['Hello']); //calling foo using window as context (this = window in global context in browser)
console.log(this.bar); //as you can see window.bar is the same as this.bar
console.log(window.bar);
var ctx = {}; //create a new context
foo.apply(ctx, ['Good night']);
console.log(ctx.bar); //ctx now has bar property that is injected from foo function
Open up your dev console to see result.
See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply