Mask a JavaScript value
Replace all characters in a string, except for the ending characters, with a mask character.
Code Articles
30 seconds of code contains a curated collection of code articles covering a wide range of development needs. The collection spans many topics, ranging from simple coding problems to theoretical concepts and development techniques.
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JavaScript · Perform math operations on arrays of numbers in JavaScript
Learn how to work with arrays of numbers in JavaScript, performing common math operations such as sum, average, product and more.
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JavaScript · How can I convert a Map to a JavaScript object and vice versa?
Learn how to convert between
Maps and objects in JavaScript. -
JavaScript · Check if an element is visible in the viewport using JavaScript
Learn how to check if an element is visible in the browser's viewport, using this simple technique.
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JavaScript · Swapcase a JavaScript string
Learn how to create a string with uppercase characters converted to lowercase and vice versa.
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JavaScript · Check if a JavaScript object has a given value or key
When working with objects, you'll often need to check if a value or key exists, and these snippets will show you how to do just that.
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JavaScript · Calculate all permutations of a JavaScript array or string
Generate all permutations of an array's elements or a string's characters using recursion.
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JavaScript · How can I inject CSS into a web page using JavaScript?
Injecting CSS into a page via JavaScript is pretty easy, if you know how to leverage the DOM.
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JavaScript · Replace the last occurrence of a pattern in a JavaScript string
Learn how to use regular expressions to replace the last occurrence of a pattern in a JavaScript string.
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JavaScript · Remove accents from a JavaScript string
Learn how to remove accents from a string in JavaScript, quickly and efficiently.
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JavaScript · How can I create a JavaScript generator function that repeats one or more values indefinitely?
Learn how to create a generator function that repeats a given value or an array of values indefinitely.
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JavaScript · Convert a string to a SEO-friendly slug with JavaScript
Learn how to easily convert any string to a SEO-friendly slug, using regular expressions.
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JavaScript · Change color lightness using JavaScript
Learn how to change the lightness component of an
hsl()color string using JavaScript. -
JavaScript · Check if two numbers are approximately equal in JavaScript
Learn how to check if two numbers are approximately equal to each other in JavaScript.
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JavaScript · How can I extend a 3-digit color code to a 6-digit color code in JavaScript?
Learn how to convert a 3-digit RGB notated hexadecimal color-code to the 6-digit form.
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JavaScript · Generate a random hex color code in JavaScript
Learn how to generate a random hexadecimal color code with a few lines of JavaScript.
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JavaScript · How can I save a JSON object to a file using JavaScript?
Learn how to write a JSON object to a file, both using Node.js and in the browser.
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JavaScript · How can I remove trailing zeros from a number in JavaScript?
When formatting decimal values in JavaScript, trailing zeros can be undesired. Here's how to deal with them.
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JavaScript · How can I partially apply a function in JavaScript?
Learn how to leverage partial application to improve the reusability of your JavaScript functions.
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JavaScript · Check if a JavaScript array has only one or many matches
Learn how to check if an array has one or more values matching the given function, and how to find the matching elements.
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JavaScript · Insert HTML string before or after element using JavaScript
Learn how to insert an HTML string before or after the start of a specified element using JavaScript.
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JavaScript · Check, compact or remove whitespaces in a JavaScript string
Learn how to work with whitespaces in JavaScript strings, using these simple yet powerful regular expression techniques.
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JavaScript · Where and how can I use memoization in JavaScript?
Learn different ways to memoize function calls in JavaScript as well as when to use memoization to get the best performance results.
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JavaScript · Check if a number is prime in JavaScript
Learn how to check if a number is prime and how to generate prime numbers up to a given number in JavaScript.