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Articles by George John
Page 18 of 79
HTML5 Geolocation in Safari 5
HTML5 Geolocation API lets you share your location with your favorite web sites. A JavaScript can capture your latitude and longitude, can be sent to backend web server, and do fancy location-aware things like finding local businesses or showing your location on a map. How Geolocation Works The Geolocation API uses navigator.geolocation to access device location. It requires user permission and works through GPS, WiFi, or IP-based positioning. Basic Syntax navigator.geolocation.getCurrentPosition(successCallback, errorCallback, options); Example: Getting Current Position Here's how to get the user's current location: ...
Read MoreHow do I clear the usage of setInterval()?
The setInterval() method executes a function repeatedly at specified intervals. Unlike setTimeout() which runs once, setInterval() continues indefinitely until cleared. Syntax let intervalId = setInterval(function, delay); Example: Basic setInterval Usage let count = 0; let intervalId = setInterval(function() { count++; console.log("Hello " + count); // Stop after 3 executions if (count === 3) { clearInterval(intervalId); ...
Read MoreHow to deal with Internet Explorer and addEventListener problem "Object doesn't support this property or method" in JavaScript?
Internet Explorer versions 8 and below don't support the standard addEventListener() method, causing the "Object doesn't support this property or method" error. This article shows how to handle cross-browser event handling. The Problem Modern browsers use addEventListener() for event handling, but older Internet Explorer versions use attachEvent() instead. Using addEventListener() directly will fail in IE8 and below. Solution 1: Using IE=edge Meta Tag Force Internet Explorer to use its latest rendering engine by adding this meta tag to your HTML head: ...
Read MoreAlternatives to HTML5 iframe srcdoc?
The HTML tag is used to create an inline frame. While the srcdoc attribute allows embedding HTML content directly, several alternatives exist for dynamically setting iframe content. Understanding iframe srcdoc The srcdoc attribute specifies HTML content to display inside an iframe without requiring an external URL. iframe srcdoc Example Alternative 1: Using contentWindow.document Access the iframe's document object directly to write content programmatically. contentWindow Alternative ...
Read MoreHTML5 tag on Android for PhoneGap application
PhoneGap is a software development framework by Adobe System, which is used to develop mobile applications. PhoneGap produces apps for all popular mobile OS platforms such as iOS, Android, BlackBerry, and Windows Mobile OS etc. HTML5 Audio support is not consistent across different devices due to codec licensing issues and OS implementation. For playing MP3 files, this can be handled by using PhoneGap's Media class that provides reliable audio programming across all platforms. Using PhoneGap Media Class The Media class provides audio recording and playback functionality. Here's how to implement basic audio playback: // Create ...
Read MoreHTML5 file uploading with multiple progress bars
HTML5 provides native file upload capabilities with progress tracking. When uploading multiple files, you can create individual progress bars for each file by leveraging the XMLHttpRequest progress events. The Challenge The main challenge is associating each XMLHttpRequest with its corresponding progress bar element. This requires storing a reference to the list item in the XMLHttpRequest object. Setting Up the Progress Tracking To track progress for multiple files, you need to bind each XMLHttpRequest to its corresponding list item element before starting the upload: Multiple File Upload with ...
Read MoreHow to make the user login for an offline web app?
Offline web apps require a different authentication approach since they can't always connect to servers. The key is implementing local authentication with data synchronization when online. How Offline Login Works When online, authenticate against the server and store user credentials locally. When offline, authenticate against the local storage instead of the remote server. User Login Online? Check Server Offline? Check Local Grant Access ...
Read MoreBootstrap Collapsible list group
To create a collapsible list group in Bootstrap, combine the panel-collapse property with the list-group property. This creates an expandable section containing a list of items that can be toggled with a click. Basic Structure A collapsible list group consists of three main components: Panel container: Wraps the entire collapsible section Panel header: Contains the clickable trigger element Collapsible content: Houses the list group items Example The following example demonstrates a collapsible list group with programming languages. Click the "Info" header to expand or collapse the list: ...
Read MoreHTML5 Canvas Font Size Based on Canvas Size
When working with HTML5 Canvas, you often need to scale font sizes dynamically based on the canvas dimensions to maintain proportional text across different screen sizes. The Problem Fixed font sizes don't adapt when canvas dimensions change, making text too small on large canvases or too large on small ones. Solution: Proportional Font Scaling Use a ratio-based approach to calculate font size relative to canvas width: var fontBase = 800; // Base canvas width var fontSize = 60; // Desired font size at base width function getFont(canvas) { ...
Read MoreIs HTML5 canvas and image on polygon possible?
Yes, it is possible to draw images on polygons in HTML5 canvas. You can achieve this by creating a pattern from an image and applying it as a fill, or by using transformation matrices to manipulate how the image is drawn within the polygon shape. Method 1: Using Image Patterns Create a pattern using the image object and set it as the fillStyle for your polygon: const canvas = document.getElementById('myCanvas'); const context = canvas.getContext("2d"); // Create an image object const img = new Image(); img.onload = function() { ...
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