JavaScript handler.has() method in JavaScript is used to “hide” any property that you want. It is a trap for in operator. It returns the Boolean value. If you want to access the property, it returns the Boolean value true; otherwise, it returns false. Whether the key was included with the original object or not.
Syntax:
const p = new Proxy(target, {
has: function(target, prop) {
}
});
Parameters: This method accepts two parameters as mentioned above and described below:
- target: This parameter is the target object.
- prop: This parameter is the property that is going to be checked for existence.
Return value: This method returns a Boolean value true if you want the property to be accessed.
Below examples illustrate the handler.has() method in JavaScript:
Example 1: In this example, we will check if the object has the values or not using the handler.has() method in JavaScript.
javascript
const handler1 = { has(target, key) { if (key[1] === '1') { return false; } return key in target; }};const monster1 = { p1roperty1: 'neveropen', property2: 4};const proxy1 = new Proxy(monster1, handler1);console.log('property2' in proxy1);console.log('p1roperty1' in proxy1);console.log('p1roperty1' in monster1); |
Output:
true false true
Example 2: In this example, we will check if the object has the values or not using the handler.has() method in JavaScript.
javascript
let s = { value: 1}let p = new Proxy(s, { has: function (target, prop) { console.log(prop); return false; }});console.log('prop' in p);let p1 = new Proxy(s, { has: function (target, prop) { console.log(prop); return true; }});console.log('prop' in p1); |
Output:
"prop" false "prop" true
Supported Browsers: The browsers supported by handler.has() method are listed below:
- Google Chrome 49 and above
- Edge 12 and above
- Firefox 18 and above
- Opera 36 and above
- Safari 10 and above
We have a complete list of Javascript Proxy/handler methods, to check those go through the Javascript Proxy/handler Reference article.