JavaScript handler.construct() method in JavaScript is a trap for the new operation and this method returns an object.
Syntax:
const p = new Proxy(target, {
construct: function(target, argumentsList, newTarget) {
}
});
Parameters: This method accepts three parameters as mentioned above and described below:
- Target: This parameter holds the target object.
- argumentsList: This parameter holds the list of the constructor.
- newTarget: This parameter holds the constructor that was originally called, p above.
Return value: This method returns an object.
Below examples illustrate the handler.construct() method in JavaScript:
Example 1: In this example, we will set a trap for an operation and return a new object using the handler.construct() method in JavaScript.
javascript
function monster1(disposition) { this.disposition = disposition;}const handler1 = { construct(target, args) { console.log('Users at Geeksforneveropen are called'); return new target(...args); }};const proxy1 = new Proxy(monster1, handler1);console.log(new proxy1('Geeks').disposition);let pro = new Proxy(function () { }, { construct: function (objTarget, args, oldConstructor) { return { Value: args[0] + " to anybody" } }})console.log(JSON.stringify(new pro("Hello "), null, ' ')) |
Output:
"Users at Geeksforneveropen are called"
"Geeks"
"{
"Value": "Hello to anybody"
}"
Example 2: In this example, we will set a trap for an operation and return a new object using the handler.construct() method in JavaScript.
javascript
const p = new Proxy(function () { }, { construct: function (target, argumentsList, newTarget) { console.log('Value: ' + argumentsList.join(', ')); return { value: argumentsList[0] * 10 / 3 }; }});console.log('New Value: ' + new p(4).value); |
Output:
"Value: 4" "New Value: 13.333333333333334"
Supported Browsers: The browsers supported by handler.construct() method are listed below:
- Google Chrome 49 and above
- Firefox 18 and above
- Opera 36 and above
- Safari 10 and above
- Edge 12 and above
We have a complete list of Javascript Proxy/handler methods, to check those go through the Javascript Proxy/handler Reference article.
