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Nalezeno "javascript": 20

Does it mutate?


This little site by Remy Sharp's makes it clear whether or not a JavaScript method changes the original array (aka mutates) or not. I was actually bitten by this the other day. I needed the last element from an array, so I remembered .pop() and used it. const arr = ["doe", "ray", "mee"]; const...

JavaScript Labels


No matter how long you’ve been a JavaScript developer, there will always be language features that you didn’t know about until you saw them in a fringe piece of code. Your reaction generally is a bit like: One of those features I see developers quizically trying to figure out...

Jak nejlépe spočítat faktoriál v JavaScriptu?


Nedávná diskuse na Facebooku mě přiměla, abych toto téma prozkoumal do větších detailů, než mi umožňovaly tamní komentáře. Tato otázka totiž kupodivu nemá jednoduchou odpověď. Když o ní začnete více přemýšlet, ponoříte se do některých zajímavějších oblastí JavaScriptu, které možná ne všichni znají

Background Sync with Service Workers


Service workers have been having a moment. In March 2018, iOS Safari began including service workers — so all major browsers at this point support offline options. And this is more important than ever — 20% of adults in the United States are without Internet at home, leaving these...

Nested Destructuring


Destructuring in JavaScript can initially feel confusing but the truth is that destructuring can make your code a bit more logical and straight forward. Destructuring does look a bit more complex when you’re looking for a property several objects deep, so let’s have a look at how to...

Force Download with JavaScript


Force download scripts have been an important part of internet usability for a long time.  I can attest to that by the number of times I’ve implemented this feature on the server side and the popularity of my PHP Force Download post, even to this day.  With the web world having...

JavaScript waitForever


Writing mochitests for new features in DevTools can be difficult and time-consuming.  There are so many elements interacting in an async manner that I oftentimes find myself using the debugger to debug the debugger!  In the case where it’s unclear what interaction isn’t working...

Get Viewport Lines and Columns in CodeMirror


CodeMirror is an amazing utility for presenting code in a browser environment.  Syntax highlighting, widgets, and a number of advanced functions make it a unique, useful tool.  When using CodeMirror inside the Firefox DevTools debugger, I found that adding hundreds of column breakpoint widgets...

Object.fromEntries


The Object object has been buffed with useful methods over the past few years.  Object.keys, Object.values, Object.freeze, and Object.assign all address frequently desired functionality.  One of the new Object methods is fromEntries, which accepts a Map or map-like array nesting and converts it...

How to Get and Set CSS Variable Values with JavaScript


CSS variables are a very welcome addition to the language, despite them being incredibly basic.  Sure we could use SASS or stylus but languages should never count on developers relying on frameworks and toolkits to accomplish what we know we need.  And just like every other part of a webpage,...

Build a state management system with vanilla JavaScript


Managing state is not a new thing in software, but it’s still relatively new for building software in JavaScript. Traditionally, we’d keep state within the DOM itself or even assign it to a global object in the window. Now though, we’re spoiled with choices for libraries and frameworks to help...

Anatomy of a malicious script: how a website can take over your browser


By now, we all know that the major tech behemoths like Facebook or Google know everything about our lives, including how often we go to the bathroom (hence all the prostate medication ads that keep popping up, even on reputable news sites). After all, we’ve given them permission to do so,...

React Node Flow


Flow, the static type checker used in many React projects, feels like a gift and a curse at times; a gift in that it identifies weaknesses in your code, and a curse that sometimes you feel like you’re needlessly adjusting your code to satisfy Flow.  I’ve grown to appreciate Flow...

Convert HTML to Markdown


One of my biggest mistakes with this blog was not finding a WordPress plugin that would allow me to write my posts with markdown; to this day I still need to write posts in “Visual” mode and then manually convert the post to HTML for “Text” mode.  One of these days I want...

Understanding the Almighty Reducer


I was reently mentoring someone who had trouble with the .reduce() method in JavaScript. Namely, how you get from this: const nums = [1, 2, 3] let value = 0 for (let i = 0; i < nums.length; i++) { value += nums[i] } ...to this: const nums = [1, 2, 3] const value = nums.reduce((ac, next)...

console.logTime


I work on a really complex debugger at Mozilla but, and don’t tell my colleagues, I sometimes enjoy simply using console.log and other console commands to get some simple output.  I know, I know, but hey — whatever gets the job done.  A few years ago I detailed console.time...

console.timeLog


I work on a really complex debugger at Mozilla but, and don’t tell my colleagues, I sometimes enjoy simply using console.log and other console commands to get some simple output.  I know, I know, but hey — whatever gets the job done.  A few years ago I detailed console.time...

Angular pro začátečníky na jsDevMeetup


V úterý 5.6. proběhne poslední přednáška před prázdninami na Fakultě informačních technologií ČVUT v Praze. Od 18:30 se v místnosti T9:107 podíváme na nový Angular a tvorbu webových aplikací. Více informací a registrace…

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