Arrow function (=>)

Examples

The short form returns the expression's result:

const double = (n) => n * 2;
 
console.log(double(4));

Output:

8

A body in curly braces needs return:

const sum = (a, b) => {
  const result = a + b;
  return result;
};
 
const makeUser = (name) => ({ name });
 
console.log(sum(2, 3));
console.log(makeUser('Anna').name);

Output:

5
Anna

An arrow function takes this from outside:

const timer = {
  seconds: 3,
  start() {
    [1, 2].forEach(() => {
      console.log(this.seconds);
    });
  },
};
 
timer.start();

Output:

3
3

Notes

To return an object in the short form wrap it in parentheses: () => ({ a: 1 }), otherwise the braces are taken as the function body.

An arrow function has no own this or arguments and cannot be called with new. That is why object methods usually use regular method syntax.