Object methods

Learn to define methods inside an object.

Object methods

When a property of an object is a function, it is called a method. In an object literal you can define methods with the shorthand: { greet() { return 'merhaba'; } }. This is the same as greet: function () { ... }.

Inside a method, the this keyword refers to the object itself. This lets you reach other properties with this.name. Example: const user = { name: 'Ayşe', greet() { return 'Merhaba ' + this.name; } }.

Call the method with a dot: user.greet(). Without parentheses you only get the function itself; to run it you need the parentheses.

Object.keys, values, entries

JavaScript provides three helpers to list an object's properties: Object.keys, Object.values and Object.entries. They live on the Object built-in, not on the object itself.

Object.keys(user) returns the property names as an array. Object.values(user) returns the values. Object.entries(user) returns an array of [name, value] pairs.

Example: Object.keys({ a: 1, b: 2 }) returns ['a', 'b']. These helpers are useful for loops and lookups.

Exercise Calculator object

Define an object named calc. Its value property is 10. Its double() method returns this.value * 2. Call the method and print the result with console.log.

Show example solution

const calc = { value: 10, double() { return this.value * 2; } };
console.log(calc.double());

Test yourself

What does this refer to inside a method?
- The global object
- The function itself
- A new object
- The object the method belongs to
Show answer

The object the method belongs to — this refers to the object the method was called on.

Reach with this

const user = { name: 'Ayşe', greet() { return 'Merhaba ' + this.____; } };

Show answer

const user = { name: 'Ayşe', greet() { return 'Merhaba ' + this.name; } };

Match the Object helpers

Object.keys(o)

Names array
Object.values(o)

Values array
Object.entries(o)

Name-value pairs
o.method()

Method call

Next lesson: Object spread

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