Both freeze and seal are used to create non-extensible objects in JavaScript, but there are plenty of differences between them.
- Object.seal() allows changes to the existing properties of an object. It prevents from deletion of existing properties but cannot prevent them from external changes.
- Object.freeze() does not allow so. It makes an object immune to everything even little changes cannot be made.
Syntax:
Object.seal(objectname);
Object.freeze(objectname);
Example 1: This example, depicts how Object.seal() is used to create a non-extensible object, but that does not prevent the value of the object to be changed and it is seen that the value gets updated to 20.
javascript
// creates an objectlet obj = { // assigns 10 to value value: 10};// creates a non-extensible objectObject.seal(obj);// the value gets updated to 20obj.value = 20;console.log(obj.value); |
Output:
20
Example 2: This example, depicts how Object.freeze() is used to create a non-extensible object, but where the existing value of the object is prevented from being changed and 10 is given as the output.
javascript
let obj = { // assigns 10 to value value: 10};// creates a non-extensible objectObject.freeze(obj);// updates the valueobj.value = 20;// but cannot change the existing valueconsole.log(obj.value); |
Output:
10
Let us see the differences in a tabular form:
|
freeze |
seal |
|---|---|
| It is used to prevent the object from adding new properties | It is used to make the properties of an object non-configurable. |
| It is also used so that the current existing properties should not be modified | It is also used so that the new properties do not get added |
| It takes a parameter as an object | It takes parameters as an object |
| Its return type is of the object type. | Its return type is e-sealed object type. |
