Example var person = { firstName: “John”, lastName : “Doe”, id : 5566, fullName : function() { return this.firstName + ” ” + this.lastName; } }; Try it Yourself » What is “this”? In a function definition, this refers to the “owner” of the function. In the example above, this refers to the person object. The person object “owns” the fullName method. Default Binding When used alone, this refers to the Global object. In a browser the Global object is […]
“use strict”; Defines that JavaScript code should be executed in “strict mode”. The “use strict” Directive The “use strict” directive is new in JavaScript 1.8.5 (ECMAScript version 5). It is not a statement, but a literal expression, ignored by earlier versions of JavaScript. The purpose of “use strict” is to indicate that the code should be […]
Hoisting is JavaScript’s default behavior of moving declarations to the top. JavaScript Declarations are Hoisted In JavaScript, a variable can be declared after it has been used. In other words; a variable can be used before it has been declared. Example 1 gives the same result as Example 2: Example 1 x = 5; // Assign 5 to x […]
Errors can (will) happen, every time you write some new computer code. Code Debugging Programming code might contain syntax errors, or logical errors. Many of these errors are difficult to diagnose. Often, when programming code contains errors, nothing will happen. There are no error messages, and you will get no indications where to search for […]
The try statement lets you test a block of code for errors. The catch statement lets you handle the error. The throw statement lets you create custom errors. The finally statement lets you execute code, after try and catch, regardless of the result. Errors Will Happen! When executing JavaScript code, different errors can occur. Errors can be coding errors made by the programmer, […]
A regular expression is a sequence of characters that forms a search pattern. The search pattern can be used for text search and text replace operations. What Is a Regular Expression? A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this […]
JavaScript Bitwise Operators Operator Name Description & AND Sets each bit to 1 if both bits are 1 | OR Sets each bit to 1 if one of two bits is 1 ^ XOR Sets each bit to 1 if only one of two bits is 1 ~ NOT Inverts all the bits << Zero […]
Number() converts to a Number, String() converts to a String, Boolean() converts to a Boolean. JavaScript Data Types In JavaScript there are 5 different data types that can contain values: string number boolean object function There are 3 types of objects: Object Date Array And 2 data types that cannot contain values: null undefined The […]
Loops can execute a block of code as long as a specified condition is true. The While Loop The while loop loops through a block of code as long as a specified condition is true. Syntax while (condition) { code block to be executed } Example In the following example, the code in the […]
Loops can execute a block of code a number of times. JavaScript Loops Loops are handy, if you want to run the same code over and over again, each time with a different value. Often this is the case when working with arrays: Instead of writing: text += cars[0] + “<br>”; text += cars[1] + “<br>”; text […]
he switch statement is used to perform different actions based on different conditions. Switch Statement Use the switch statement to select one of many code blocks to be executed. Syntax switch(expression) { case n: code block break; case n: code block break; default: code block } This is how it works: The switch […]
Conditional statements are used to perform different actions based on different conditions. Conditional Statements Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this. In JavaScript we have the following conditional statements: Use if to specify a block of code to […]
Comparison and Logical operators are used to test for true or false. Comparison Operators Comparison operators are used in logical statements to determine equality or difference between variables or values. Given that x = 5, the table below explains the comparison operators: Operator Description Comparing Returns Try it == equal to x == 8 false Try it » x […]
A JavaScript Boolean represents one of two values: true or false. Boolean Values Very often, in programming, you will need a data type that can only have one of two values, like YES / NO ON / OFF TRUE / FALSE For this, JavaScript has a Boolean data type. It can only take the values true or false. The Boolean() Function You can […]
Math.random() Math.random() returns a random number between 0 (inclusive), and 1 (exclusive): Example Math.random(); // returns a random number Try it Yourself » Math.random() always returns a number lower than 1. JavaScript Random Integers Math.random() used with Math.floor() can be used to return random integers. Example Math.floor(Math.random() * 10); // returns a random integer from 0 to […]
The JavaScript Math object allows you to perform mathematical tasks on numbers. Example Math.PI; // returns 3.141592653589793 Try it Yourself » Math.round() Math.round(x) returns the value of x rounded to its nearest integer: Example Math.round(4.7); // returns 5 Math.round(4.4); // returns 4 Try it Yourself » Math.pow() Math.pow(x, y) returns the value of x to the power of […]
Set Date methods let you set date values (years, months, days, hours, minutes, seconds, milliseconds) for a Date Object. Set Date Methods Set Date methods are used for setting a part of a date: Method Description setDate() Set the day as a number (1-31) setFullYear() Set the year (optionally month and day) setHours() Set the […]
There are generally 3 types of JavaScript date input formats: Type Example ISO Date “2015-03-25” (The International Standard) Short Date “03/25/2015” Long Date “Mar 25 2015” or “25 Mar 2015” The ISO format follows a strict standard in JavaScript. The other formats are not so well defined and might be browser specific. JavaScript Date Output […]
JavaScript Date Output By default, JavaScript will use the browser’s time zone and display a date as a full text string: Thu Jul 05 2018 12:12:01 GMT+0500 (Pakistan Standard Time) You will learn much more about how to display dates, later in this tutorial. Creating Date Objects Date objects are created with the new Date() constructor. There […]
The sort() method sorts an array alphabetically: Example var fruits = [“Banana”, “Orange”, “Apple”, “Mango”]; fruits.sort(); // Sorts the elements of fruits Try it Yourself » Reversing an Array The reverse() method reverses the elements in an array. You can use it to sort an array in descending order: Example var fruits = [“Banana”, “Orange”, “Apple”, “Mango”]; fruits.sort(); // First sort the elements of fruits fruits.reverse(); // Then reverse the […]
