Question

I’m not sure the correct term for this. But I want to write a function that accepts another function and execute it.
For eg.

function test(data, aFunc) {
   var newData = data + " Shawn";

   aFunc.call(newData);
}

test("hello", function(data){
   alert(data);
});

Data is supposed to contain “hello Shawn” string. Help me rewrite this the correct way please.

Answer 1

The first argument of the call method is used to set the this keyword (the function context) explicitly, inside the invoked function, e.g.:

function test(data, aFunc) {
   var newData = data + " Shawn";

   aFunc.call(newData);
}

test("hello", function () {
   alert(this); // hello Shawn
});

If you want to invoke a function without caring about the context (the this keyword), you can invoke it directly without call:

function test(data, aFunc) {
   var newData = data + " Shawn";

   aFunc(newData); // or aFunc.call(null, newData);
}

test("hello", function (data) {
   alert(data);
});

Note that if you simply invoke a function like aFunc(newData); or you use the call or apply methods with the this argument set as null or undefined, the this keyword inside the invoked function will refer to the Global object (window).