job.answiz.com
  • 0
Votes
name

What is the difference between using call and apply to invoke a function?

var func = function() {
  alert('hello!');
};

func.apply(); vs func.call();

Are there performance differences between the two aforementioned methods? When is it best to use call over apply and vice versa?

The difference is that apply lets you invoke the function with arguments as an array; callrequires the parameters be listed explicitly. A useful mnemonic is "A for array and C for comma."

See MDN's documentation on apply and call.

Pseudo syntax:

theFunction.apply(valueForThis, arrayOfArgs)

theFunction.call(valueForThis, arg1, arg2, ...)

There is also, as of ES6, the possibility to spread the array for use with the call function, you can see the compatibilities here.

Sample code:

 

function theFunction(name, profession) {
    console.log("My name is " + name + " and I am a " + profession +".");
}
theFunction("John", "fireman");
theFunction.apply(undefined, ["Susan", "school teacher"]);
theFunction.call(undefined, "Claude", "mathematician");
theFunction.call(undefined, ...["Matthew", "physicist"]); // used with the spread operator
  • 1
Reply Report