Javascript Tutorials and Examples

Javascript – check if string is number

The isNaN() function determines whether a value is NaN (Not-A-Number) or not. Note that parseInt approach may not work with strings having valid number prefix. read more

Javascript – parseInt

The parseInt() function parses a string argument and returns an integer of the specified radix (default 10). In case the string starts with a valid read more

Javascript – string ends with check

ECMAScript 6 String.prototype.endsWith() method can be used to check if a string ends with a suffix. But it is not yet supported by all browsers. read more

Javascript – string starts with check

ECMAScript 6 String.prototype.startsWith() method can be used to check if a string starts with something. But it is not yet supported by all browsers. Another read more

Javascript array forEach

Few notes on Javascript array forEach Array arr is passed to function as local variable a Array arr is also available in function here as read more

Javascript – append item to array

Javascript code to append one or multiple values at the end of array Append one value Append multiple values

Javascript – remove last item from array

Javascript code to remove last item from array using arr.pop() Append one value

Javascript – prepend item to array

Javascript code to prepend an item at the beginning of array using arr.unshift() Prepend one value to array

Javascript – remove first item from array

Javascript code to remove first item from array using arr.shift() Remove first item from array

Javascript – create array from 0 to N-1 in nodejs

In Javascript to create an array of number from 0 to n-1, we can use spread operator. It is part of ECMAScript (version 6). Currently read more

Javascript convert array to json string

JSON.stringify() can be used to convert a given javascript value to json strng. Usage: JSON.stringify(value[, replacer[, space]]) Here are some examples Example – JSON.stringify() default read more

Javascript for-in loop to iterate over keys of javascript object

for in loop over javascript associative array for in loop over javascript DOM object

Javascript – DOM appendChild example

Javascript DOM method appendChild can be used to append a child to existing DOM element. For example it can be used to append an Image, read more

Javascript – get computed style of an element

To get computed style of an element the following approaches can be taken: Vanilla javascript: window.getComputedStyle(element) jQuery: .css(propName) Example – computed style using Javascript Example read more

Javascript – how to view text inside DOM element

Javascript DOM method textContent can be used to get the text content inside a DOM. This can be useful to obtain content from a web read more

Javascript – img onload examples

Sometime we need to call a function after an image has been loaded. We can attach onload even handler on image either in html itself read more

Javascript – ready vs on load event handler example

HTML document ready event is called before image assets, etc. are loaded on the page. window onload handler is called once all assets have been read more

Javascript – use querySelector to set dom element html

Javascript querySelector can be used to select and set html of a dom element using css selectors. This can be done with jQuery also. But read more

Javascript DOMContentLoaded listener example

DOMContentLoaded event is fired when document DOM is ready and before images, etc. are loaded. It is similar to jQuery $(document).ready(). Here is code snippet read more

Javascript event bubble vs capture

Javascript/HTML events can propagate in two ways in DOM API. This is relevant when more than one element are listening on same event. Event propagation read more

Javascript how to stop event propagation

Javascript/HTML event can be handled by more than one dom elements and after one handler, it propagate to next element. API Event.stopPropagation() can be used read more

Javascript onscroll event handler

Javascript onscroll event handler can be attach to any DOM element. Attaching it to document is a typical use case. But it can be attached read more

Javascript onscroll event handler with throttling

Javascript onscroll event handler is called on every onscroll event. At times we want to ensure that it is not called again before a certain read more

Make an element draggable using Vanilla Javascript

Javascript event handler mousedown and mousemove can be used to make an element draggable without using any other library. This can be made to work read more

Multiple onload handlers using vanilla Javascipt

Attaching a function to windows on load event can be done in multiple ways using plain vanilla Javascript. One option is to use wondow.onload where read more

Use universal selector to get all DOM nodes in vanilla Javascript

The universal selector (*), matches the name of any element type. It matches any single element in the document tree. Some ways it can be read more

document querySelector examples

Javascript querySelector() and querySelectorAll() can be used to get DOM element based on given CSS selector. These works on document and element objects both. querySelector() read more

Javascript – dump all handlers on window object

DOM window object has many javascript event handlers attached to it. It may be handy to dump and view all of these. Here is code read more

Are Javascript functions objects?

A Javascript function is also an object of type function. So it can be used as an object and can have member variables. Also note read more

Javascript – declare and invoke anonymous function at the same time

Javascript can declare anonymous function and call it at the same time using the following syntax: (function (arg1, arg2, …) { }) (arg1, arg2, …); read more

HTML5 drag and drop – move an element to dropzone

HTML5 Drag and Drop interfaces enable applications to use drag and drop (using mouse) features in web browser. It involves dragging an element and dropping read more

Using JSLint on command line on Ubuntu linux – quick start guide

Sometimes javascript is developed and tested by pushing it to the website and then checking if it is working in browser as intended. If your read more

Javascript – call vs apply

Javascript call() and apply() can be used to invoke a function. They are mostly same. The only difference is in apply arguments are passed as read more

Javascript – implement class using function

Javascript classes can be created using function. Here a function can be instantiated using new keyword. The member variables and methods in function can be read more

Javascript – iterate over function arguments

Sometimes it is useful to iterate over function arguments programmatically. Function arguments can be access using arguments variable. Here is code snippet for this. Note read more

Javascript – print all methods of an object

To print all methods of an object, we can use Object.getOwnPropertyNames and check if the corresponding value is a function. The Object.getOwnPropertyNames() method returns an read more

Javascript – run a function at regular interval

Javascript setInterval can be used to make repeated calls to a function or code with fixed interval. If there is a possibility that function logic read more

Javascript – textarea and text input select all

Javascript can bse used to select full text in textarea and text put fields in HTML. Example – select all in textarea Example – read more

Javascript arrow function examples

Arrow (=>) function expressions are shorter syntax compared to function expressions. Arrow functions are always anonymous. Here are some commonly used usage syntax patterns. singleParam read more

Javascript check if variable is defined

Code snippet to check if a given javascript variable is defined. This also covers a variable having null value and non existing entry in an read more

Javascript local and global variables

Javascript variables can be local or global scoped depending upon how the are declared. In HTML all global scoped variables becomes part of window object. read more

Javascript parse json string

JSON.parse() can be used to parse a given json string into javascript value (array, string, etc.) Here are some examples Example – parse json containing read more

Javascript prototype examples

Javascript function can be used to define classes. Inside classes, member properties (containing functions, objects, etc.) can be defined either as member variables in constructor read more

Javascript settimeout example

Javascript setTimeout can be used to scheduled a function or code to run at a specified delay. This is pretty powerful API and can be read more

Javascript sleep implementation

Javascript does not have any sleep function. At times (e.g. to simulate a specific situation) we may need to sleep or delay the code for read more

Requirejs – quickstart guide for beginners

RequireJS is a JavaScript file and module loader. It can be used in browsers and other javascript environments like Node. This article is intended as read more

Javascript – catch errors using window.onerror

Javascript errors can be caught using window.onerror event handler. Whenever a javascript error occurs browser calls this function. In this tutorial we’ll write error handler read more

How to print javascript object to log

Often we need to print a javascript object to console log or somewhere else for debugging purpose. These are some handy ways to dump javascript read more

Javascript – Number function

The Number JavaScript object is a wrapper object allowing you to work with numerical values. A Number object is created using the Number() constructor. It read more