The alert() method displays an alert box with a message and an OK button. The alert() method is used when you want information to come through to the user.

JavaScript has three kind of popup boxes: Alert box, Confirm box, and Prompt box. Alert Box An alert box is often used if you want to make sure information comes through to the user.

Alert messages can be used to notify the user about something special: danger, success, information or warning. × Danger! Indicates a dangerous or potentially negative action.

JS Alert (alert.js) The alert plugin include options and methods to close alert messages. For a tutorial about Alerts, read our Bootstrap Alerts Tutorial.

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JavaScript Function Syntax. A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses (). Function names can contain letters, digits, …

The two key methods to use with JavaScript are: setTimeout(function, milliseconds) Executes a function, after waiting a specified number of milliseconds. setInterval(function, milliseconds) …

Using onload on an <img> element. Alert "Image is loaded" immediately after an image has been loaded: <img src="w3javascript.gif" onload="loadImage()" width="100" height="132">

Writing into an alert box, using window.alert(). Writing into the browser console, using console.log().

document.getElementById("myBtn").onclick = function() {myFunction()}; function myFunction() { document.getElementById("myDropdown").classList.toggle("show");}