JavaScript Tutorials

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    Intl.NumberFormat

    Formatting numbers on the client side is an important task, especially when you consider how much raw API usage is in play these days. What's also important is ensuring those numbers are meaningful to users, no matter where they are in the world, especially if...

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    Detect CSS Overflow Elements

    Every once in a while you encounter a CSS annoyance that takes some cleverness to discover. One such case rears its ugly head in unwanted and unexpected scrollbars. When I see unwanted scrollbars, I usually open developer tools, click the element inspector, and hover...

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    Use Logpoints!

    There's sometimes a tribal attitude about how web developers should be debugging their code and solving problems. There's the console.log loyalists, then there's the debugger/breakpoint maximalists. I worked on the Firefox DevTools debugger for years and I can tell you my philosophy -- use...

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    JavaScript Wake Lock API

    An enjoyable web apps rely on engineers implementing the APIs that cover all of the small things. Those small things sometimes improve performance, usability, accessibility, and the app's relationship with its host system. The Wake Lock API is the latter -- an API...

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    navigator.clipboard API

    Interacting with a user's host clipboard is something web developers have wanted for both good and evil purposes. On the good side, it's nice to allow users to easily copy text like wallet addresses or branch names; for evil, copying malicious text that the user...

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    Return a Default Value with Promises Using catch

    Last week I tweeted all of you looking for your best JavaScript Array and Promise tricks, and as always, it didn't disappoint -- I learned quite a bit!Today's JavaScript Promise trick is brought to you by Claudio Semeraro: how to use catch to...

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    Break a forEach Loop with JavaScript

    I've written a number of blog posts about JavaScript tricks: Promise tricks, type conversion tricks, spread tricks, and a host of other JavaScript tricks. I recently ran into another JavaScript trick that blew my mind: how to break a forEach

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    React.isValidElement

    Knowing what input type you've received is hugely important in JavaScript, which is a big reason for Flow and TypeScript's rise. One such case where it's useful to know what an object represents is if the input is a string or a React element.To detect...

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    Detect Generator Functions with JavaScript

    In the current JavaScript climate of new syntaxes, features, and using loads of external libraries, it seems harder than ever to be sure what your functions are being given or even what the data represents. Of course, we've come up with Flow and TypeScript to help...

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    Node isConnected

    Every so often I discover a property in JavaScript objects that I didn't know existed, oftentimes using another trick to accomplish the same functionality. One such property I just learned about was isConnected, a node property that attached to a context (i.e. document).Here's how to...