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 <!DOCTYPE html> <html> <body> <h2>JavaScript Functions</h2> <p>This example calls a function which performs a calculation, and returns the result:</p> <p id=”demo”></p> <script> function myFunction(p1, p2) { return p1 *… Read More »
JavaScript variables can hold different data types: numbers, strings, objects and more:let length = 16; // Numberlet lastName = “Johnson”; // Stringlet 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 data types, a computer cannot… Read More »
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 / y %=… Read More »
JavaScript Arithmetic Operators Arithmetic operators perform arithmetic on numbers (literals or variables). Operator Description + Addition – Subtraction * Multiplication ** Exponentiation (ES2016) / Division % Modulus (Remainder) ++ Increment — Decrement Arithmetic Operations A typical arithmetic operation operates on two numbers. The two numbers can be literals: Example <!DOCTYPE html> <html> <body> <h2>JavaScript Arithmetic</h2>… Read More »
Example Assign values to variables and add them together:<!DOCTYPE html><html><body><h2>JavaScript Operators</h2><p>x = 5, y = 2, calculate z = x + y, and display z:</p><p id=”demo”></p><script>let x = 5;let y = 2;let z = x + y;document.getElementById(“demo”).innerHTML = z;</script></body></html> Result: JavaScript Operators x = 5, y = 2, calculate z = x + y, and… Read More »
The const keyword was introduced in ES6 (2015). Variables defined with const cannot be Redeclared. Variables defined with const cannot be Reassigned. Variables defined with const have Block Scope. Cannot be Reassigned A const variable cannot be reassigned: Example <!DOCTYPE html> <html> <body> <h2>JavaScript const</h2> <p id=”demo”></p> <script> try { const PI = 3.141592653589793; PI = 3.14; } catch (err) { document.getElementById(“demo”).innerHTML = err; } </script>… Read More »
The let keyword was introduced in ES6 (2015). Variables defined with let cannot be Redeclared. Variables defined with let must be Declared before use. Variables defined with let have Block Scope. Cannot be Redeclared Variables defined with let cannot be redeclared. You cannot accidentally redeclare a variable. With let you can not do this: Example let x = “John Doe”; let x = 0; // SyntaxError: ‘x’ has already been declared With var you can:… Read More »
4 Ways to Declare a JavaScript Variable: Using var Using let Using const Using nothing What are Variables? Variables are containers for storing data (storing data values). In this example, x, y, and z, are variables, declared with the var keyword: Example <!DOCTYPE html> <html> <body> <h1>JavaScript Variables</h1> <p>In this example, x, y, and z are variables.</p> <p id=”demo”></p> <script> var x =… Read More »
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 executed). This example… Read More »
JavaScript syntax is the set of rules, how JavaScript programs are constructed:// How to create variables:var x;let y; // How to use variables:x = 5;y = 6;let z = x + y; JavaScript Values The JavaScript syntax defines two types of values: Fixed values Variable values Fixed values are called Literals. Variable values are called Variables. JavaScript Literals The two most important syntax… Read More »