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8 Best JavaScript One-Liners

Shivam Singh on September 15, 2023

Hey everyone! If you're new to coding, you're probably excited but maybe a little overwhelmed, right? Don't sweat it! 😅 Today, we're going to look ...

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Jon Randy 🎖️ • Sep 15 '23 • Edited

3) can be shorter:

const sortBy = (arr, key) => arr.sort((a, b) => a[key] > b[key] || -1)

5) You have not shown how to use the function, and it will only delay the execution of code chained with the Promise. Statements immediately after will proceed as normal with no delay.

6) Your input is missing the key.

7) Your input shown is wrong, and this can also be shorter - using the built-in method designed for the purpose:

const insert = (arr, index, newItem, a=[...arr]) => (a.splice(index, 0, newItem), a)

8) Will not function correctly as it will never return #ffffff, and also many other colours as you are not padding the string with leading zeroes. A correct version:

const randomColor = "#" + (~~(Math.random() * 8**8)).toString(16).padStart(6,0)

Ski • Sep 18 '23 • Edited

#3: when sorting numbers just use subtraction for numbers just do a - b for ascending order

arr.sort((a, b) => a[key] - b[key])

and for strings use a.localeCompare(b)

Shivam Singh • Sep 18 '23

Yes, this is also correct!

Shivam Singh • Sep 15 '23

1. The `chill` Function

You're correct; my initial example did not show how to actually use the function in a meaningful way. It's a Promise-based function, so you'd typically use it with async/await or .then() to actually cause a delay in the code's execution. Here's how you could use it:

(async () => {
  console.log("Before waiting");
  await chill(2000);
  console.log("After waiting for 2 seconds");
})();

2. The `sortBy` Function

You bring up a good point. The function could indeed be simplified to:

const sortBy = (arr, key) => arr.sort((a, b) => a[key] > b[key] ? 1 : -1);

This approach assumes that a[key] and b[key] will never be equal if sorting is based on unique identifiers, which might be okay for some cases but not all.

3. The `pluck` Function

You're right; the input was incomplete without specifying the key. A more full example could be:

const pluck = (arr, key) => arr.map(obj => obj[key]);
console.log(pluck([{x: 1}, {x: 2}], 'x')); // Output: [1, 2]

4. The `insert` Function

Your point is valid; the input example could have been more complete. Also, your shorter version using splice is more concise. However, one benefit of the original slice approach is that it does not mutate the original array.

const insert = (arr, index, newItem, a=[...arr]) => (a.splice(index, 0, newItem),a);

5. The `randomColor` Function

You are correct again; the original version can indeed skip some colors and never reach #FFFFFF. Your version with padding zeros is more accurate in generating the full spectrum of colors:

const randomColor = "#" + (~~(Math.random() * 8**8)).toString(16).padStart(6,0);

Thank you for pointing out these details; your observations are insightful and enhance the accuracy and efficiency of the examples.
I will update it according to it!

Jon Randy 🎖️ • Sep 15 '23 • Edited

Try the shorter sortBy with repeated identifiers. Works just fine. If the two identifiers are equal it makes no difference what order they are sorted in.

My splice example doesn't mutate the original array.

Jon Randy 🎖️ • Sep 15 '23

Might want to fix the glaring typo in the header image too! 😉

Shivam Singh • Sep 15 '23

@jonrandy which one?

Jon Randy 🎖️ • Sep 15 '23

"8 One-Linear You Will Love"

Shivam Singh • Sep 15 '23 • Edited

ohh yes you are correct! 😊
I am open for any other suggestions

Shivam Singh • Sep 15 '23

1. The `sortBy` Function with Repeated Identifiers

You're right that if two elements have the same identifier, the order doesn't matter for those particular elements. In many sorting algorithms, including JavaScript's native .sort(), elements that compare as equal remain in their original order (stable sort). So, your simplified version is equally effective:

const sortBy = (arr, key) => arr.sort((a, b) => a[key] > b[key] ? 1 : -1);

This will work just fine even with repeated identifiers.

2. The `splice` Example and Array Mutation

I apologize for the misunderstanding. You're correct; your example using splice actually doesn't mutate the original array because you made a shallow copy (a=[...arr]) before applying the splice.

Here's the function for clarity:

const insert = (arr, index, newItem, a=[...arr]) => (a.splice(index, 0, newItem),a);

In this function, a=[...arr] creates a new array that is a copy of the original arr. Then, splice is called on this new array (a), so the original arr remains unchanged. Therefore, it is a non-mutating operation on the original array.

Thank you for your keen observations; they serve to improve the quality and accuracy of the discussion.

Danny Engelman • Sep 16 '23

My favorite oneliner when building Web Components, or any DOM is:

const element=(t,p={})=>Object.assign(document.createElement(t), p);

Click the Result tab:

Shivam Singh • Sep 18 '23

Great!

Ski • Sep 18 '23 • Edited

Please never do #4: comparing using JSON.stringify(a) == JSON.stringify(b). It's very poor practice: it doesn't guarantee correctness - in some cases it can give false positive as well as false negative (for instance objects equal but key order is not JSON stringify will produce different output) - as some objects might not get stringified at all, and some values can even result into json.stringify throwing an error.

If you have class objects, then good idea is to implement equal() method on your object and compare a.equal(b). For generic object use recursive algorithm.

But more importantly consider why do you need deep equality check in first place - as it can be computationally intensive. Likely there should be ways to avoid it in first place.

Shivam Singh • Sep 18 '23

Yes it doesn't give a correct solution for every scenario

José Pablo Ramírez Vargas • Sep 15 '23

While I'm not saying that all of these suffer from it, this is the kind of programming that leads to performance hell. People get so used to shorthand versions of things (mostly loop-based), that end up enumerating collections an enormously unnecessary amount of times.

This is also found in .Net and the LINQ advocates.

Bottom line: Shorter is more commonly worse than you think. Analyze your algorithms thoroughly.

Shivam Singh • Sep 16 '23 • Edited

It's not totally correct. It depends

Lucas • Sep 15 '23

Great, I think it would be useful to also comment that it can happen that objects with the same values still return false when compared with stringify method due to the order of their properties

Shivam Singh • Sep 15 '23

yes correct!

James Graça-Jones • Sep 20 '23

Thanks for the article, I definitely learnt a lot from this! I slightly worry that some of the wording in Point 4 distracts the reader from realising that just because two arrays have the same values doesn't mean they actually are the same. They aren't the same object, for example, they just have the same values in them. Fun article though :)

Shivam Singh • Sep 21 '23

thanks

Ariel Mejia • Sep 18 '23

Hi @shivamblog If it makes sense to you I would add a one-liner to shuffle and pick items from an array:

const randomizeArray = () => [...array].sort(() => 0.5 - Math.random()).slice(0, items);

Shivam Singh • Sep 19 '23

what is items here?

Ariel Mejia • Sep 19 '23

@shivamblog Sorry items could be the number of items so you can shuffle and also get only some of them:

and the array should be the array to shuffle and slice it.

const randomizeArray = () => [...array].sort(() => 0.5 - Math.random()).slice(0, numberOfItems);

Shivam Singh • Sep 19 '23

Then it is correct!

Tobiasss97 • Sep 15 '23

Great post

Shivam Singh • Sep 15 '23

thanks!

1. The chill Function

2. The sortBy Function

3. The pluck Function

4. The insert Function

5. The randomColor Function

1. The sortBy Function with Repeated Identifiers

2. The splice Example and Array Mutation

1. The `chill` Function

2. The `sortBy` Function

3. The `pluck` Function

4. The `insert` Function

5. The `randomColor` Function

1. The `sortBy` Function with Repeated Identifiers

2. The `splice` Example and Array Mutation