How to Delete Property from Object in JavaScript: Simple Guide

To delete a property from an object in JavaScript, use the delete operator followed by the object and property name, like delete object.property. This removes the property from the object entirely.

Syntax

The delete operator removes a property from an object. The syntax is:

• delete object.property - deletes the property named property from object.
• delete object['property'] - alternative syntax using bracket notation.

After deletion, the property no longer exists on the object.

javascript

delete object.property;
delete object['property'];

Example

This example shows how to delete a property from an object and check the result.

javascript

const person = {
  name: 'Alice',
  age: 30,
  city: 'New York'
};

console.log('Before delete:', person);
delete person.age;
console.log('After delete:', person);
console.log('Age property exists?', 'age' in person);

Output

Before delete: { name: 'Alice', age: 30, city: 'New York' }
After delete: { name: 'Alice', city: 'New York' }
Age property exists? false

Common Pitfalls

Some common mistakes when deleting properties:

• Trying to delete a variable or a property declared with var, let, or const will not work.
• Deleting properties from objects created with Object.freeze() or with non-configurable properties fails silently or throws errors in strict mode.
• Using delete on array elements removes the element but leaves empty holes; use array methods instead.

javascript

const obj = { a: 1 };

// Wrong: deleting a variable
// let a = 10;
// delete a; // false, does not delete variable

// Right: deleting object property
console.log(delete obj.a); // true
console.log(obj); // {}

Output

true
{}

Quick Reference

Summary tips for deleting properties:

• Use delete object.property to remove a property.
• Check property existence with 'property' in object after deletion.
• Do not use delete on variables or constants.
• For arrays, prefer methods like splice() over delete.

Key Takeaways

Use the delete operator to remove a property from an object: delete object.property.

Deleted properties no longer exist on the object and return false when checked with 'in'.

Do not use delete on variables or constants; it only works on object properties.

Deleting array elements with delete leaves holes; use array methods like splice instead.

Properties that are non-configurable or frozen cannot be deleted.