Comment by Ben Aston on In JavaScript, how can I conditionally assign value...
const { lastName } = objA || objB;: objA is truthy, and so it is the result of the OR operator. And it doesn't have a lastName property, hence the destructured variable lastName remains undefined.
View ArticleComment by Ben Aston on In JavaScript, how can I conditionally assign value...
OR returns the first truthy operand, or the second falsy operand
View ArticleComment by Ben Aston on JavaScript Date - How to better set midnight UTC+0
If you want to treat everything as UTC, and if you can get the raw day, month, year values out of the date picker, the Date constructor assumes UTC when supplied with a string with no time component;...
View ArticleComment by Ben Aston on JAVASCRIPT Reload a page or a div using JS
location.reloadwill not bypass the browser's cache.
View ArticleComment by Ben Aston on js count coming up as Nan within html elements
NaN is produced when a string is converted to a Number, but that string does not contain a parseable number. Check for this.
View ArticleComment by Ben Aston on How to use vanilla script to bounce elements from...
Create two elements. Position them absolutely so you have precise control over their location on the page. Use getClientBouningRect to determine the precise location of the edges of the element. Use...
View ArticleComment by Ben Aston on setInterval's interval always changes to 1 second...
There are a bunch of reasons why an interval might be longer than expected. They are outlined here. setInterval follows the same rules as setTimeout.
View ArticleComment by Ben Aston on How to wait a function to finish completely before...
You probably need to promisify downloadVideo and return the promise (with resolve linked to the exit event).
View ArticleComment by Ben Aston on Why can I use an arrow function before it's declared...
In the first example, invocation of settingsDataAvailable(...) occurs at minimum one microtask later due to the presence of an await. This means that the synchronous top-level evaluation of the entire...
View ArticleComment by Ben Aston on Should I use px or rem value units in my CSS?
While it is true that browser "zooming" technique changed over the years, having a relative font-size (like rem) is not about zooming per-se: it's about user style sheets and their effect. People with...
View ArticleComment by Ben Aston on Is it possible to store a button value from a click...
A callback function is only run when a button is pressed. In your first example, the console.log is evaluated before any button is pressed, and is therefore printing undefined.
View ArticleComment by Ben Aston on What is the point of void operator in JavaScript?
You're dancing on the head of a pin about ES1.3 vs JS1.3? Wow. oreilly.com/library/view/javascript-the-definitive/059600048‌​0/…
View ArticleImporting styles into a web component
What is the canonical way to import styles into a web component?The following gives me an error HTML element <link> is ignored in shadow tree:<template><link rel="style" href="foo.css"...
View ArticleAnswer by Ben Aston for Sorting javascript object by number (value), then abc...
Using the clever technique found in another answer:const words = {"be": 3,"a": 5,"an": 3}const sortedEntries = (o) => Object.entries(words) .sort(([k1, v1], [k2, v2]) => v2 - v1 ||...
View ArticleAnswer by Ben Aston for Please Explain how the below javascript code
Pipe is an operation that accepts zero or more functions and returns a function that invokes those functions in a "chain", passing the result of each function to the next. So multiply6 will be a...
View ArticleAnswer by Ben Aston for How to trim out a sub string value
String#replace accepts a regular expression. For example 👇const s = '9:00:10 AM'const t = '12:10:20 AM'console.log(s.replace(/:\d{1,2}[ ]{1}/, '')) // 9:00 AMconsole.log(t.replace(/:\d{1,2}[ ]{1}/,...
View ArticleAnswer by Ben Aston for Is variable initialization also hoisted in JavaScript
TLDRIn JavaScript, both variable and function declarations are hoisted.Initialization is not.Hoisting means that - regardless of the lexical position of declaration - the identifier is semantically...
View ArticleSubmitting a form using a custom button using HTML Web Components
I have defined a custom DOM element, but when placed inside a form, it does not submit it. How can I get the form to submit when I click the button?<form action="/foo" method="GET"><my-button...
View ArticleAnswer by Ben Aston for How to wait a function to finish completely before...
You probably need to promisify downloadVideo.Something like this will download one video at a time, sequentially. Untested, of course.const downloadCmd = (id) => `yt-dlp -f bestaudio --extract-audio...
View ArticleAnswer by Ben Aston for Is it possible to store a button value from a click...
In your first example, the console.log is being evaluated before any button is pressed, and will therefore print undefined.To print a meaningful value, the logging of the choice must occur after a...
View ArticleAnswer by Ben Aston for Creating functions using `Object.create`
It is not possible.Object.create is merely a convenience function to configure prototype chains and define own properties.The key distinguishing characteristic of functions is the existence of the...
View ArticleWhat are the disadvantages of using this asynchronous logging code?
Some code I just wrote follows. It demonstrates applying a PostSharp aspect to a method for the purposes of recording the duration of the method invocation in an asynchronous manner - so that if the...
View ArticleStateful custom hook
I have a component, StatusIndicator, that uses a Redux Toolkit query, q, to fetch a status value and display it.I want to write a custom hook, usePolling, that can be configured using arguments to...
View ArticleASP.NET, determine if a request content type is for JSON
I'd like to implement an extension method IsJsonRequest() : bool on the HttpRequestBase type. In broad terms what should this method look like and are there any reference implementations?This is a...
View ArticleWhat is the purpose of these comments in Babel output?
Babel transpilation output follows. What is the purpose of generated comments like /*#__PURE__*/?function foo() { return (<div><p></p><p></p></div>)}transpiles...
View ArticleAnswer by Ben Aston for How to execute a function after another function has...
I think what you are looking for is a rate limiter function. Best to search NPM for a library, but I implemented such a function below.The following code configures an array to hold the timestamps of...
View ArticleEnabling auto-completion in git bash on windows?
I would like to be able to typegit checkout <start-of-branch-name>...and then hit tab and have the branch name autocomplete for me. How can I enable this?
View Article[[Class]] property in JavaScript objects
The [[Class]] property of object is set according to how an object is created IIUC. Is this why some objects are rendered to the Chrome console in a meaningful way e.g. MyFoo and others are simply...
View ArticleChaining promises returned from a generator function
I want to chain the promises returned by a generator function.I am expecting this to print:started...result is: initial valueresult is: waited for 10msresult is: waited for 20msdoneBut it...
View ArticleWhy does this async generator cause the JavaScript runtime to hang?
The following JavaScript causes the runtime to hang on Chrome (v80.0.3987.116) and Firefox (v72.0.2) on OSX 10.15.2.Why?Note that I am marking the iterator function as async.const iterable = { async...
View ArticleComment by Ben Aston on On a memory level, is there a difference between...
@MichaelVigato You'd have to look at engine source code IMO. Classes provide an alternative way to coordinate object instantiation, most of which is simply an encoding of specific steps that could be...
View ArticleHow do I apply a skin tone to an emoji in JavaScript?
Given this emoji, how can I programmatically apply a skin tone in JavaScript?Grinning face is 0x1F600.Dark Skin Tone is 0x1F3FF.Do I simply concatenate the values together?The following code, based on...
View ArticleAnswer by Ben Aston for Insert a string at a specific index
Instantiate an array from the stringUse Array#spliceStringify again using Array#joinThe benefits of this approach are two-fold:SimpleUnicode code point compliantconst pair =...
View ArticleWhat is reentrancy in JavaScript?
I would like to improve my understanding of the word reentrant.Is this function reentrant?function* foo() { yield 1; yield 2;}And this one?function foo() { return 1;}And this one?var x = 0;function...
View ArticleOn a webpage can I hijack the vertical scrolling action and make it horizontal?
On a webpage can I hijack the vertical scrolling action and make it horizontal?Please try and ignore the potential usability issues.
View ArticleWhen should I use yield* vs yield in redux-saga?
I want to call another saga from a saga.The saga is of course a generator function, and is asynchronous.Should I ever user yield * or should I always use yield?function* mySaga({ payload: { id, name }...
View ArticleChrome timeline - how can I determine the cause of a "Recalculate Style" log...
Profiling a page with the built-in timeline recorder in Chrome, I see repeated "Recalculate Style" entries. They have no obvious information to link them to DOM element or event.How can I best...
View ArticleIs it possible to make a callable object non-callable?
In JavaScript, functions are callable.Can I remove this attribute from a function, leaving only a normal object?var foo = function () {};foo.[[callable]] = false; // pseudocodefoo(); // "foo is not a...
View ArticleEscape a space in a file path string [closed]
I receive a file path string via JSON.parse, but I need to escape the spaces in the string with backslashes.How should I do this idiomatically in Javascript?For example:var input = JSON.parse('{...
View ArticleIs it possible to wrap a setInterval in an async generator function?
Without using the Streams API, is it possible to wrap a setInterval in an async generator function, to simulate a never-ending stream?I know how to do it using setTimeout to supply the delay.Using...
View ArticleIs scope.$apply synchronous in AngularJS?
Is the following code synchronous in AngularJS?scope.$apply(function(){ console.log('foo');});
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