Extract first 3 letters from each word in JavaScript string and add underscore separator

[FlyingLeaf]

I need help with string manipulation in JavaScript. I have a sentence like this:

let sentence = "Good morning beautiful world";

I want to transform it so it becomes:

"GOO_MOR_BEA_WOR"

Basically I want to grab the first three letters from every word, make them uppercase, and put an underscore between each group. I already know how to make letters uppercase with .toUpperCase() but I’m stuck on the rest of the logic. How can I split the words, take only the first 3 characters from each, and then join them back with underscores?

[Hazel_27Yoga]

Just chain the string methods together. Split the sentence into words, map over each word to grab the first 3 characters and uppercase them, then join with underscores.

let sentence = "Good morning beautiful world";
let result = sentence.split(' ').map(word => word.substring(0, 3).toUpperCase()).join('_');
console.log(result); // "GOO_MOR_BEA_WOR"

Substring’s great here - it won’t break if a word’s shorter than 3 characters, just returns the whole word. I use this pattern all the time for making short IDs from longer text.

[JumpingMountain]

Watch out for edge cases depending on what you’re doing. If your string has extra spaces or empty strings, filter them out first with sentence.split(' ').filter(word => word.length > 0) before mapping. I hit this when processing user input with messy spacing. Also think about punctuation - ‘hello, world!’ will grab the comma and exclamation in your 3-character slice. For clean results, strip non-alphabetic characters first with a regex replace.

[Luke_Brilliant]

u could even use slice instead of substring if u like. both do the same thing with positive indexes, but slice feels cleaner to me. the split > map > join way is def the best approach tho - solid solution!