Latest Javascript Tutorials and How-To's

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Checking for a Sub-String in Javascript - All Possible Cases

Javascript provides multiple methods that can check whether a sub-string is contained in a string, depending on various possible use-cases.
June 9, 2020
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How to Check If a Javascript Function Was Called Using new Operator

The new.target property can be used to detect whether a function was invoked as a constructor using the new operator, or just called normally.
May 20, 2020
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File Uploading Progress in Javascript Fetch

Currently it is not possible to get file upload progress for fetch. The alternate solution for now is to use XMLHttpRequest.
May 16, 2020
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How to Check If Element is Visible / Hidden in Page using Intersection Observer

Checking whether an element is visible or hidden in the full page, even through it may not be in screen view, can be done through an Intersection Observer. The trick is to set the root element to document.documentElement.
May 14, 2020
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How to Detect Change in Element Size with Javascript

Detecting an element for change in dimensions using JS can be done with the ResizeObserver interface. This is supported in all modern browsers.
May 11, 2020
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Detecting Dark Mode with Javascript

Device dark mode can be checked in Javascript by using window.matchMedia() to check a match for the prefers-color-scheme: dark CSS media query.
May 9, 2020
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Getting Property Value in a Deeply Nested Object (using ES2020 Optional Chaining Operator)

Property value in a deeply nested Javascript object can be found using the Optional Chaining Operator, introduced in ES2020.
May 4, 2020
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Handling Error HTTP Responses in Javascript fetch

Failed HTTP responses can be handled in fetch() by checking whether the returned Promise was rejected due to a network error. Subsequently the Response.ok property needs to be checked for an invalid HTTP status code.
April 27, 2020
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Creating a Slider / Carousel with CSS Flexbox (with infinite repeating items in loop)

A responsive slider / carousel can be created with CSS flexbox using the order property. Items can be repeated infinitely in a circular loop by changing the order property each time.
April 25, 2020
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Reading a Text File from Server using JavaScript

A text file on a server can be read with Javascript by downloading the file with Fetch / XHR and reading the response as text.
April 22, 2020
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Javascript File Uploading with Fetch, Async & Await

Javascript fetch method can be used to upload files to server. fetch is Promise-based, so we can use async / await to write synchronous styled functions.
April 13, 2020
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Checking If CSS Property Supported in Current Browser with Javascript

With newer CSS properties not available in all browsers, it is sometimes required to check whether a CSS property & its value are supported in the current browser. This can be detected in Javascript using the CSS.supports() method.
March 13, 2020
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Get Random Numbers, Cryptographically Secure, in Javascript

Random numbers that are cryptographically strong, can be generated in Javascript using the Web Crypto API.
March 9, 2020
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Using formdata Event for AJAX Form Submissions

The newly introduced formdata event can enable the Javscript FormData object to participate in form submissions. When trying to submit a form via AJAX, this is helpful to include custom elements in the request.
February 3, 2020
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Dynamically Rotating an Image using Javascript

An image can be rotated with Javascript by dynamically changing its CSS transform property. The point around which rotation needs to happen can be specified with the transform-origin property.
January 15, 2020
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Managing the URL Hash with Javascript

The Javascript URL object can be used to get and set hash value of a given url. To detect a change in hash in the current url, the hashchange event can be listened to.
January 12, 2020
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Reading a File and Getting its Binary Data in Javascript

The binary data of a local file selected by the user can be retrieved using the readAsBinaryString method of a FileReader object.
January 9, 2020
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How to Check if Cookies are Enabled or Disabled

Without cookies being enabled in the browser, some web applications may not work as expected. To prevent such cases navigator.cookieEnabled property can be used to do a prior check whether cookies are enabled or not.
January 5, 2020
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Checking for a Secure Context Before Running User Sensitive Code

Browsers allow user-sensitive and low-level web APIs to execute only when the page is in a secure context. In addition, the window.isSecureContext property can be used to check whether the current environment is safe or not.
January 2, 2020
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Filling an Array with a Given Value in Javascript

The Array.fill() method can be used to fill an array with a specific value, starting from a given index and ending upto another index.
December 21, 2019