JavaScript strings are used for storing and manipulating text. JavaScript Strings A JavaScript string is zero or more characters written inside quotes. Example var answer = “It’s alright”; var answer = “He is called ‘Johnny’”; var answer = ‘He is called “Johnny”‘; Try it Yourself » String Length The length of a string is found in the built in property length: Example […]
HTML events are “things” that happen to HTML elements. When JavaScript is used in HTML pages, JavaScript can “react” on these events. HTML Events An HTML event can be something the browser does, or something a user does. Here are some examples of HTML events: An HTML web page has finished loading An HTML input field was changed An […]
Scope determines the accessibility (visibility) of variables. JavaScript Function Scope In JavaScript there are two types of scope: Local scope Global scope JavaScript has function scope: Each function creates a new scope. Scope determines the accessibility (visibility) of these variables. Variables defined inside a function are not accessible (visible) from outside the function. Local JavaScript […]
Real Life Objects, Properties, and Methods In real life, a car is an object. A car has properties like weight and color, and methods like start and stop: Object Properties Methods car.name = Fiat car.model = 500 car.weight = 850kg car.color = white car.start() car.drive() car.brake() car.stop() All cars have the same properties, but the property values differ from car to car. All […]
A JavaScript function is a block of code designed to perform a particular task. A JavaScript function is executed when “something” invokes it (calls it). Example function myFunction(p1, p2) { return p1 * p2; // The function returns the product of p1 and p2 } Try it Yourself » JavaScript Function Syntax A JavaScript function is defined […]
JavaScript Data Types JavaScript variables can hold many data types: numbers, strings, objects and more: var length = 16; // Number var lastName = “Johnson”; // String var x = {firstName:”John”, lastName:”Doe”}; // Object The Concept of Data Types In programming, data types is an important concept. To be able to operate on variables, it is important to know something about the type. Without […]
JavaScript Assignment Operators Assignment operators assign values to JavaScript variables. Operator Example Same As = x = y x = y += x += y x = x + y -= x -= y x = x – y *= x *= y x = x * y /= x /= y x = x […]
JavaScript Arithmetic Operators Arithmetic operators perform arithmetic on numbers (literals or variables). Operator Description + Addition – Subtraction * Multiplication / Division % Modulus (Remainder) ++ Increment — Decrement Arithmetic Operations A typical arithmetic operation operates on two numbers. The two numbers can be literals: Example var x = 100 + 50; Try it Yourself » or variables: Example […]
Example Assign values to variables and add them together: var x = 5; // assign the value 5 to x var y = 2; // assign the value 2 to y var z = x + y; // assign the value 7 to z (x + y) Try it Yourself » The assignment operator (=) assigns a value to a variable. Assignment var x = 10; Try […]
JavaScript variables are containers for storing data values. In this example, x, y, and z, are variables: Example var x = 5; var y = 6; var z = x + y; Try it Yourself » From the example above, you can expect: x stores the value 5 y stores the value 6 z stores the value 11 Much Like […]
JavaScript comments can be used to explain JavaScript code, and to make it more readable. JavaScript comments can also be used to prevent execution, when testing alternative code. Single Line Comments Single line comments start with //. Any text between // and the end of the line will be ignored by JavaScript (will not be […]
JavaScript syntax is the set of rules, how JavaScript programs are constructed: var x, y; // How to declare variables x = 5; y = 6; // How to assign values z = x + y; // How to compute values JavaScript Values The JavaScript syntax defines two types of values: Fixed values and variable values. Fixed values are called literals. Variable values […]
Example var x, y, z; // Statement 1 x = 5; // Statement 2 y = 6; // Statement 3 z = x + y; // Statement 4 Try it Yourself » JavaScript Programs A computer program is a list of “instructions” to be “executed” by a computer. In a programming language, these programming instructions are called statements. A JavaScript program is a list of programming statements. In […]
JavaScript Display Possibilities JavaScript can “display” data in different ways: Writing into an HTML element, using innerHTML. Writing into the HTML output using document.write(). Writing into an alert box, using window.alert(). Writing into the browser console, using console.log(). Using innerHTML To access an HTML element, JavaScript can use the document.getElementById(id) method. The id attribute defines the HTML element. The innerHTML property defines the HTML content: […]
The <script> Tag In HTML, JavaScript code must be inserted between <script> and </script> tags. Example <script> document.getElementById(“demo”).innerHTML = “My First JavaScript”; </script> Try it Yourself » Old JavaScript examples may use a type attribute: <script type=”text/javascript”>. The type attribute is not required. JavaScript is the default scripting language in HTML. JavaScript Functions and Events A JavaScript function is […]
This page contains some examples of what JavaScript can do. JavaScript Can Change HTML Content One of many JavaScript HTML methods is getElementById(). This example uses the method to “find” an HTML element (with id=”demo”) and changes the element content (innerHTML) to “Hello JavaScript”: document.getElementById(“demo”).innerHTML = “Hello JavaScript”; Try it Yourself » JavaScript accepts both double and single […]
Images can improve the design and the appearance of a web page. HTML Images Syntax In HTML, images are defined with the <img> tag. The <img> tag is empty, it contains attributes only, and does not have a closing tag. The src attribute specifies the URL (web address) of the image: <img src=”url“> The alt Attribute The alt attribute provides an alternate text for an […]
HTML List Example An Unordered List: Item Item Item Item An Ordered List: First item Second item Third item Fourth item Try it Yourself » Unordered HTML List An unordered list starts with the <ul> tag. Each list item starts with the <li> tag. The list items will be marked with bullets (small black circles) by default: Example <ul> […]
Every HTML element has a default display value depending on what type of element it is. The default display value for most elements is block or inline. Block-level Elements A block-level element always starts on a new line and takes up the full width available (stretches out to the left and right as far as […]
Using The class Attribute The class attribute specifies one or more class names for an HTML element. The class name can be used by CSS and JavaScript to perform certain tasks for elements with the specified class name. In CSS, to select elements with a specific class, write a period (.) character, followed by the name of […]
