Description

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Advanced · 12 min

Method calls and this

Understand the call receiver and preserve it when passing a method.

Use the call receiver

For an ordinary method called as object.method(), this refers to that object. The function declaration alone does not permanently bind a receiver.

const user = { name: "Ada", greet() { return `Hello, ${this.name}`; } };
console.log(user.greet());

Output

Hello, Ada

Bind a callback

bind() returns a function with a fixed this value. Use it when a method needs its object after being passed as a callback.

const counter = { value: 4, read() { return this.value; } };
const read = counter.read.bind(counter);
console.log(read());

Output

4

Put it into practice

  1. Predict each result before running the example.
  2. Complete the coding task, then explain why your solution works.

Try it yourself

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Keep the receiver

Bind read to counter before calling it, then display its result.

Practice