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Javascript Object preventExtensions() Method

Javascript Object preventExtensions() Method with example on javascript, object, getOwnPropertyDescriptor(), getOwnPropertyDescriptors(), defineProperties(), defineProperty(), entries(), freeze(), javascript tutorial, javascript array etc.

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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:

Object.preventExtensions(obj)

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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