how to call a function in javascript – The call() method is a predefined JavaScript method. It is used to call a function contains this value and an argument provided individually.
how to call a function in javascript
The call() method is used to write methods for different objects. there are main 4 ways to call a function in JavaScript. As a function, As a method, As a constructor and via call and apply.
Calling a function as a function
<button onclick="welcomeMessage()">great welcome</button> <script> function welcomeMessage() { console.log(this); console.log(arguments); console.log('welcome'); } </script>
force the context to be undefined
<button onclick="welcomeMessage()">great welcome</button> <script> 'use strict'; function welcomeMessage() { console.log(this); console.log(arguments); console.log('welcome'); } </script>
Calling a function as a method
<button onclick="SetProfile.welcomeMessage()">great welcome</button> <script> SetProfile = { welcomeMessage: function () { console.log(this); console.log(arguments); console.log('welcome'); } }
Calling a function as a constructor
<input type="text" id="name"></input> <button onclick="welcomeMessage()">great welcome</button> <script> function SetProfile(name) { console.info('start level constructor'); console.log(this); console.log(arguments); this.name = name; console.info('end constructor') } function welcomeMessage() { var name = document.getElementById('name').value; var resdata = new SetProfile(name); console.log('welcome ' + resdata.name); } </script>
Don’t Miss : Call Javascript Function From Html
Calling a function via call and apply
<button onclick="go()">GO</button> <script> var member = []; var name = 'deep'; function Person(queryIndex) { queryIndex % 2 === 0 ? this.name = 'deep ' + queryIndex : this.name = 'mobi ' + queryIndex; } function displayProfile() { console.log(this.name); } function go() { //call displayProfile to print the name variable defined on the window object displayProfile(); //populate the member array with a couple of member for (let queryIndex = 0; queryIndex < 5; queryIndex++) { member.push(new Person(queryIndex)); } // lets call the displayProfile for each object that we just created // seting this dynamically member.forEach(p => { displayProfile.call(p); }); // displayProfile.call(valueOfThis, 1, 2, 3); // displayProfile.apply(valueOfThis, [1, 2, 3]) } </script>
//call accepts a list of values displayProfile.call(valueOfThis, 1, 2, 3); //apply accepts an array of values displayProfile.apply(valueOfThis, [1, 2, 3]);
I hope you get an idea about how to call a function in javascript.
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