#falsy

[techiio]

Ask a question on any technology-related topic; start a thread, enter an ongoing discussion thread or answer them just at Techiio. Get answers from several perspectives of industry experts.

[booklover250197]

"In describing this siren, singing and smiling, coaxing and cajoling, the author, with modest pride, asks his readers all round, has he once forgotten the laws of pliteness, and showed the monster's hideous tail above water? No! Those who like may peep down under waves that are pretty tranparent, and see it writhing and twirling, diabolically hideous and slimy, flapping amongst bones, or curling round corpses; but above the waterline, I ask, has not everything been proper, agrreable and decorous, and has any the most squeamish moralist in Vanity Fair a right to cry fie? When however, the siren disappears and dives below, down among the dead men, the water of course grows turbid over her, and it is labour lost to look into it ever so curiously. They look pretty enough when they sit upon a rock, twanging their harps and combing their hair, and sing, and beckon to you to come and hold the looking-glass; but when they sink into their native element, depend on it those mermaids are about no good, and we had best not examine the fiendish marine cannibals, revelling and feasting on their wretched pickled victims."

(W. M. Thackeray, Vanity fair, pp. 620-621)

[brandontom]

Know Your Babel Plugins: The Optional Chaining Proposal

The Optional Chaining proposal introduces a new operator that allows you take advantage of chaining even when the shape of an object is not guaranteed. #babeljs #knowyourbabelplugins

In this series, I’ll be going over the ins-and-outs of the various plugins for Babel, the popular JavaScript transpiler. I’m going to assume you know a thing or two about Babel, NPM, and JavaScript.

The Optional Chaining proposal introduces a new operator that allows you take advantage of chaining even when the shape of an object is not guaranteed. This reduces the amount of defensive coding…

View On WordPress

[lines-of-code]

When falsy values betray you....

Things like this can quickly lead to your NodeJS memory being filled with multiple GB of empty arrays and crashing your Node Application, so watch out!

ytvids is an array that has an amount of x entries. subytids is an empty array.

Basically what I wanted to do here is take ytvids and split it into multiple arrays with the defined length of 50 entries each. .splice is destructive, meaning it removes elements from the array permanently compared to it's sister method .slice, which only gives back the entries but doesn't take them out of the array

var array = ["A", "B", "C"]; console.log(array.slice(0, 2)); // => ["A", "B"] console.log(array); // => ["A", "B", "C"] console.log(array.splice(0, 2)); // => ["A", "B"] console.log(array); // => ["C"]

So what this loop is supposed to do is splice out up to 50 entries every time the code in the loop runs and add the new array to the subytids array. And the code runs because an array is considered a truthy value in JS. So it runs and it splices and it runs and it splices. But someday, the array will be empty and splicing only returns []. What I did not consider is that an empty array actually STILL counts as a truthy value. Meaning the loop does not stop. And it keeps pushing and pushing empty arrays coming from .splice to subytids. Up to the point that there is just too much memory in the heap and it crashes.

What I ACTUALLY should have done in the first place, is use while (ytvids.length). Length is the number of items in an array and that counts down after each splicing. 0 in JS is considered a falsy value and breaks the loop when no more entries are remaining in the array.

There is only a handful of things that are considered falsy in JS, so you might want to remember those:

false (boolean)

null

undefined

0

NaN

'' or "" (empty strings)

document.all (although this is rarely used apart from detecting IE)

[conceptlog]

Falsy

In JavaScript, there are primitive value types: strings ("hello world"), numbers (23), booleans (false), null, or undefined. While only a boolean value can be fully true or false, the other types, when queried for truth or falsity, will evaluate to one or the other. A string, for example, evaluates to true; null evaluates to false. These "implied" boolean values cause the type to be what's called "truthy" or "falsy."