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JavaScript Object.preventExtensions() MethodThe 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:
Example 1const uu = {}; Object.preventExtensions(uu); console.log( Object.isExtensible(uu) ); Output: false Example 2const obj = {}; Object.preventExtensions(obj); obj.o = 3; console.log( obj.hasOwnProperty("o") ); Output: false Example 3const t = {"p":3}; Object.preventExtensions(t); delete t.p; console.log ( t.hasOwnProperty ( "p" ) ); //expected output: false Output: false
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