The Object.preventExtensions() method in JavaScript is a standard built-in object which checks whether an object is extensible or not(i.e. if we can add new properties to the object or not).
Syntax:
Object.isExtensible( obj )
Parameters: This method accepts a single parameter as mentioned above and described below:
- obj: This parameter holds the object which should be checked for extensibility.
Return value: This method returns a Boolean value indicating if the given object is extensible or not.
The below examples illustrate the Object.isExtensible() Method in JavaScript:
Example 1: In this example, we will check if new properties can be added to an object or not using the Object.isExtensible() Method in JavaScript. The output is a Boolean value.
javascript
const neveropen1 = {}; console.log(Object.isExtensible(neveropen1)); Object.preventExtensions(neveropen1); console.log(Object.isExtensible(neveropen1)); const neveropen2 = {}; Object.preventExtensions(neveropen2); console.log( Object.isExtensible(neveropen2) ); |
Output:
true false false
Example 2: In this example, we will check if new properties can be added to an object or not using the Object.isExtensible() Method in JavaScript. The output is a Boolean value.
javascript
let neveropen1 = {}; console.log(Object.isExtensible(neveropen1)); console.log(Object.preventExtensions(neveropen1)); console.log(Object.isExtensible(neveropen1)); let neveropen2 = Object.seal({}); console.log(Object.isExtensible(neveropen2)); let neveropen3 = Object.freeze({}); console.log(Object.isExtensible(neveropen3)); |
Output:
true [object Object] false false false
We have a complete list of Javascript Object methods, to check those please go through this JavaScript Object Complete Reference article.
Supported Browsers: The browsers supported by Object.isExtensible() method are listed below:
- Google Chrome 6 and above
- Edge 12 and above
- Firefox 4 and above
- Internet Explorer 9
- Opera 12 and above
- Safari 5.1 and above
