JavaScript | handler.isExtensible() Method
The handler.isExtensible() method in JavaScript is a trap for Object.isExtensible() method and it returns a boolean value.
Syntax:
const p = new Proxy(target, {
isExtensible: function(target) {
}
});Parameters: This method accept single parameter as mentioned above and described below:
- target: This parameter is the target object.
Return value: This method returns a Boolean value.
Below examples illustrate the handler.isExtensible() method in JavaScript:
Example 1:
javascript
<script>const monster1 = { canEvolve: true};const handler1 = { isExtensible(target) { return Reflect.isExtensible(target); }, preventExtensions(target) { target.canEvolve = false; return Reflect.preventExtensions(target); }};const proxy1 = new Proxy(monster1, handler1);document.writeln(Object.isExtensible(proxy1));document.writeln("<br>");document.writeln(monster1.canEvolve);document.writeln("<br>");document.writeln(Object.preventExtensions(proxy1));document.writeln("<br>");document.writeln(Object.isExtensible(proxy1));document.writeln("<br>");document.writeln(monster1.canEvolve); </script> |
Output:
true true [object Object] false false
Example 2:
javascript
<script>const p = new Proxy({}, { isExtensible: function(target) { console.log('isExtensible method'); return true; }});console.log(Object.isExtensible(p));var a = { canEvolve: true }; var b = { isExtensible(target) { return true; }, }; const proxy1 = new Proxy(a, b); console.log(Object.isExtensible(proxy1));</script> |
Output:
"isExtensible method" true true
Supported Browsers: The browsers supported by handler.isExtensible() method are listed below:
- Google Chrome 49 and above
- Edge 12 and above
- Firefox 31 and above
- Opera 36 and above
- Safari 10 and above
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