JavaScript Object.preventExtensions() Method

The Object.preventExtensions() only prevents the addition of new properties from ever being added to an object (i.e., prevents future extensions to the object). This change is a permanent that means once an object has been made non-extensible, it cannot make extensible again.

Syntax:

Parameter:

obj: It is the object which should be made non-extensible.

Return value:

It returns the object being made non-extensible.

Browser Support:

Chrome	6
Edge	Yes
Firefox	4
Opera	12

Example 1

const uu = {};
Object.preventExtensions(uu);
console.log(
    Object.isExtensible(uu)
); 

Output:

false

Example 2

 const obj = {};
Object.preventExtensions(obj);
obj.o = 3;

console.log(
    obj.hasOwnProperty("o")
); 

Output:

false

Example 3

const t = {"p":3};
Object.preventExtensions(t);
delete t.p;
console.log ( t.hasOwnProperty ( "p" ) );
//expected output: false

Output:

false

Next TopicJavaScript Objects

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