js how to create immutable objects-1024programmer

The immutability of objects means that we don’t want objects to change in any way after creation (making them read-only types).

Suppose we need to define a car object and use its properties throughout the project to perform operations. We cannot allow any data to be incorrectly modified.

const myTesla = {
  maxSpeed: 155,
  batteryLife: 300,
  weight: 2300
 };

Object.preventExtensions() prevents extensions

This method prevents adding new properties to existing objects, preventExtensions() is an irreversible operation, We can never add extra properties to objects again.

Object.isExtensible(myTesla); // true
 Object. preventExtensions(myTesla);
 Object. isExtensible(myTesla); // false
 myTesla.color = 'blue';
 console.log(myTesla.color) // undefined

Object.seal() seals

It prevents adding or removing properties, seal() also Can prevent property descriptors from being modified.

Object.isSealed(myTesla); // false
 Object. seal(myTesla);
 Object.isSealed(myTesla); // true

 myTesla.color = 'blue';
 console.log(myTesla.color); // undefined

 delete myTesla. batteryLife; // false
 console.log(myTesla.batteryLife); // 300

 Object.defineProperty(myTesla, & #39;batteryLife'); // TypeError: Cannot redefine property: batteryLife

Object.freeze() Freeze

It works the same as Object.seal(), and it makes the property unwritable.

Object.isFrozen(myTesla); // false
 Object. freeze(myTesla);
 Object.isFrozen(myTesla); // true

 myTesla.color = 'blue';
 console.log(myTesla.color); // undefined

 delete myTesla. batteryLife;
 console.log(myTesla.batteryLife); // 300

 Object.defineProperty(myTesla, & # 39; batteryLife & # 39;); // TypeError: Cannot redefine property: batteryLife

 myTesla. batteryLife = 400;
 console.log(myTesla.batteryLife); // 300

Note: If you want an error to be thrown when trying to modify an immutable object, use strict mode.

Recommended tutorial: js introductory tutorial

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