The element you were trying to find wasn’t in the DOM when your script ran. The position of your DOM-reliant script can have a profound effect on its behavior. Browsers parse HTML documents from top to bottom. Elements are added to the DOM and scripts are (generally) executed as they’re encountered. This means that order … Read more
The difference is that functionOne is a function expression and so only defined when that line is reached, whereas functionTwo is a function declaration and is defined as soon as its surrounding function or script is executed (due to hoisting). For example, a function expression: // TypeError: functionOne is not a function functionOne(); var functionOne … Read more
A closure is a pairing of: A function and A reference to that function’s outer scope (lexical environment) A lexical environment is part of every execution context (stack frame) and is a map between identifiers (i.e. local variable names) and values. Every function in JavaScript maintains a reference to its outer lexical environment. This reference … Read more
One does not simply redirect using jQuery jQuery is not necessary, and window.location.replace(…) will best simulate an HTTP redirect. window.location.replace(…) is better than using window.location.href, because replace() does not keep the originating page in the session history, meaning the user won’t get stuck in a never-ending back-button fiasco. If you want to simulate someone clicking … Read more
Introduction Asynchronous code is a type of programming that allows multiple tasks to be executed simultaneously. This type of code can be difficult to debug, as it can be difficult to determine why a variable is not being altered after it has been modified inside of a function. In this article, we will discuss the … Read more
One word answer: asynchronicity. Forewords This topic has been iterated at least a couple of thousands of times, here, in Stack Overflow. Hence, first off I’d like to point out some extremely useful resources: @Felix Kling’s answer to “How do I return the response from an asynchronous call?”. See his excellent answer explaining synchronous and … Read more
What you should know about this this (aka “the context”) is a special keyword inside each function and its value only depends on how the function was called, not how/when/where it was defined. It is not affected by lexical scopes like other variables (except for arrow functions, see below). Here are some examples: function foo() … Read more
Introduction “Use strict” is a directive that is used to enable strict mode in JavaScript. Strict mode is a way to opt-in to a restricted variant of JavaScript that helps to catch common coding mistakes and prevent them from becoming bugs. It is a way to ensure that code is written in a more secure … Read more
Update for ES6 modules Inside native ECMAScript modules (with import and export statements) and ES6 classes, strict mode is always enabled and cannot be disabled. Original answer This article about Javascript Strict Mode might interest you: John Resig – ECMAScript 5 Strict Mode, JSON, and More To quote some interesting parts: Strict Mode is a … Read more
Well, the problem is that the variable i, within each of your anonymous functions, is bound to the same variable outside of the function. ES6 solution: let ECMAScript 6 (ES6) introduces new let and const keywords that are scoped differently than var-based variables. For example, in a loop with a let-based index, each iteration through … Read more
Since the question refers to a single element, this code might be more suitable: // Checks CSS content for display:[none|block], ignores visibility:[true|false] $(element).is(“:visible”); // The same works with hidden $(element).is(“:hidden”); It is the same as twernt’s suggestion, but applied to a single element; and it matches the algorithm recommended in the jQuery FAQ. We use … Read more
Find the index of the array element you want to remove using indexOf, and then remove that index with splice. The splice() method changes the contents of an array by removing existing elements and/or adding new elements. const array = [2, 5, 9]; console.log(array); const index = array.indexOf(5); if (index > -1) { // only … Read more
→ For a more general explanation of asynchronous behaviour with different examples, see Why is my variable unaltered after I modify it inside of a function? – Asynchronous code reference → If you already understand the problem, skip to the possible solutions below. The problem The A in Ajax stands for asynchronous. That means sending … Read more
You can change the timezone with the offset at the end of the date string (e.g. -05:00). And then create the date string you want using get functions. You will need to pad the month, day, hour and minutes. However, the .get (eg .getMonth) functions return numbers, so you will also have to convert them … Read more
The value you’re looking at, is seconds from epoch. It is not a duration, but actually a date. In JavaScript, you may convert this value to milliseconds from epoch, and construct a date object out of it. See the following snippet: var secondsFromEpoch = 1518292800; var millisFromEpoch = secondsFromEpoch * 1000; var date = new … Read more