JavaScript Strings A JavaScript string stores a series of characters like “John Doe”. A string can be any text inside double or single quotes: var carname = “Volvo XC60”; var carname = ‘Volvo XC60’; String indexes are zero-based: The first character is in position 0, the second in 1, and so on. For a tutorial about Strings, read our JavaScript […]
JavaScript Statements In HTML, JavaScript statements are “instructions” to be “executed” by the web browser. This statement tells the browser to write “Hello Dolly.” inside an HTML element with id=”demo”: Example document.getElementById(“demo”).innerHTML = “Hello Dolly.”; Try it Yourself » For a tutorial about Statements, read our JavaScript Statements Tutorial. JavaScript Statement Identifiers JavaScript statements often start with a statement […]
RegExp Object A regular expression is an object that describes a pattern of characters. Regular expressions are used to perform pattern-matching and “search-and-replace” functions on text. Syntax /pattern/modifiers; Example var patt = /dwfaisalabad/i Example explained: /dwfaisalabad/i is a regular expression. dwfaisalabad is a pattern (to be used in a search). i is a modifier […]
JavaScript operators are used to assign values, compare values, perform arithmetic operations, and more. JavaScript Arithmetic Operators Arithmetic operators are used to perform arithmetic between variables and/or values. Given that y = 5, the table below explains the arithmetic operators: Operator Description Example Result in y Result in x Try it + Addition x = y […]
JavaScript Numbers JavaScript has only one type of number. Numbers can be written with, or without, decimals: Example var x = 3.14; // A number with decimals var y = 34; // A number without decimals Extra large or extra small numbers can be written with scientific (exponent) notation: Example var x = 123e5; // 12300000 var y = 123e-5; // 0.00123 For a tutorial about JavaScript […]
Math Object The Math object allows you to perform mathematical tasks. Math is not a constructor. All properties/methods of Math can be called by using Math as an object, without creating it. Syntax var x = Math.PI; // Returns PI var y = Math.sqrt(16); // Returns the square root of 16 For a tutorial about the Math object, read […]
JSON (JavaScript Object Notation) JSON is a format for storing and transporting data. JSON is text, and text can be transported anywhere, and read by any programming language. JavaScript Objects can be converted into JSON, and JSON can be converted back into JavaScript Objects. This way we can work with the data as JavaScript objects, with no complicated […]
The JavaScript global properties and functions can be used with all the built-in JavaScript objects. JavaScript Global Properties Property Description Infinity A numeric value that represents positive/negative infinity NaN The NaN property represents “Not-a-Number” value. This property indicates that a value is not a legal number. The NaN property is the same as the Number.Nan […]
Error Object The Error object provides error information when an error occurs. Example In this example we have written “alert” as “adddlert” to deliberately produce an error. Return the error name and a description of the error: try { adddlert(“Welcome”); } catch(err) { document.getElementById(“demo”).innerHTML = err.name + “<br>” + err.message; } Try it Yourself » For a tutorial about JavaScript […]
JavaScript Booleans JavaScript booleans can have one of two values: true or false. The Boolean() Function You can use the Boolean() function to find out if an expression is true: Example Boolean(10 > 9) // returns true Try it Yourself » Or even easier: Example (10 > 9) // also returns true 10 > 9 // also returns true Try it Yourself » For […]
Array Object The Array object is used to store multiple values in a single variable: var cars = [“Saab”, “Volvo”, “BMW”]; Array indexes are zero-based: The first element in the array is 0, the second is 1, and so on. For a tutorial about Arrays, read our JavaScript Array Tutorial. Array Properties Property Description constructor Returns the function that […]
The HTML DOM NodeList Object A NodeList object is a list (collection) of nodes extracted from a document. A NodeList object is almost the same as an HTMLCollection object. Some (older) browsers return a NodeList object instead of an HTMLCollection for methods like getElementsByClassName(). All browsers return a NodeList object for the property childNodes. Most browsers return a NodeList […]
The HTMLCollection Object The getElementsByTagName() method returns an HTMLCollection object. An HTMLCollection object is an array-like list (collection) of HTML elements. The following code selects all <p> elements in a document: Example var x = document.getElementsByTagName(“p”); The elements in the collection can be accessed by an index number. To access the second <p> element you can write: y […]
Adding and Removing Nodes (HTML Elements) Creating New HTML Elements (Nodes) To add a new element to the HTML DOM, you must create the element (element node) first, and then append it to an existing element. Example <div id=”div1″> <p id=”p1″>This is a paragraph.</p> <p id=”p2″>This is another paragraph.</p> </div><script> var para = document.createElement(“p”); var node = document.createTextNode(“This is new.”); […]
With the HTML DOM, you can navigate the node tree using node relationships. DOM Nodes According to the W3C HTML DOM standard, everything in an HTML document is a node: The entire document is a document node Every HTML element is an element node The text inside HTML elements are text nodes Every HTML attribute […]
The addEventListener() method Example Add an event listener that fires when a user clicks a button: document.getElementById(“myBtn”).addEventListener(“click”, displayDate); Try it Yourself » The addEventListener() method attaches an event handler to the specified element. The addEventListener() method attaches an event handler to an element without overwriting existing event handlers. You can add many event handlers to […]
HTML DOM allows JavaScript to react to HTML events: Reacting to Events A JavaScript can be executed when an event occurs, like when a user clicks on an HTML element. To execute code when a user clicks on an element, add JavaScript code to an HTML event attribute: onclick=JavaScript Examples of HTML events: When a […]
Learn to create HTML animations using JavaScript. A Basic Web Page To demonstrate how to create HTML animations with JavaScript, we will use a simple web page: Example <!DOCTYPE html> <html> <body><h1>My First JavaScript Animation</h1><div id=”animation”>My animation will go here</div></body> </html> Try it Yourself » Create an Animation Container All animations should be relative to a container […]
The HTML DOM allows JavaScript to change the style of HTML elements. Changing HTML Style To change the style of an HTML element, use this syntax: document.getElementById(id).style.property = new style The following example changes the style of a <p> element: Example <html> <body><p id=”p2″>Hello World!</p><script> document.getElementById(“p2”).style.color = “blue”; </script> <p>The paragraph above was changed by a script.</p> </body> </html> Try […]
The HTML DOM allows JavaScript to change the content of HTML elements. Changing the HTML Output Stream JavaScript can create dynamic HTML content: Date: Sun Oct 14 2018 14:15:06 GMT+0500 (Pakistan Standard Time) In JavaScript, document.write() can be used to write directly to the HTML output stream: Example <!DOCTYPE html> <html> <body><script> document.write(Date()); </script></body> </html> Try it […]
