Split string by index in JavaScript using direct way like splitting by a regex

Question

This is kind of a challenge, as I'm sure there must be a better way to do this but I'm not able to find it.

Given a string, I want to split it into two strings by a given index. For instance:

input: 
  - string: "helloworld"
  - index: 5
output: ["hello", "world"]

An easy way is to make two slices, but isn't there a more direct way like splitting by a regex or something? I would like to achieve my purpose with a single instruction.

The non-elegant way:

const str = "helloworld";
const [ str1, str2 ] = [ str.substring(0, 5), str.substring(5) ];

Dupe doesn't look like what OP is looking for here as OP already knows how to use slice or substring — anubhava
– anubhava, Commented Oct 19, 2022 at 6:45
@anubhava The accepted answer with the highest vote-count is the same as your "Alternative" o.O — Andreas
– Andreas, Commented Oct 19, 2022 at 7:22
But it is not the main solution which is using split besides IMO dupe marking has to be on the nature of the problem not the similarity of an answer. — anubhava
– anubhava, Commented Oct 19, 2022 at 7:50

anubhava · Accepted Answer · 2022-10-19 07:54:28Z

3

You can use this regex for splitting:

(?<=^.{5})

Here (?<=^.{5}) is a lookbehind assertion that splits at the position that has 5 characters on left hand side after start.

Code:

var s = 'helloworld';

var arr = s.split(/(?<=^.{5})/);

console.log(arr);
//=> ['hello', 'world']

Alternatively, you can use match + slice:

s.match(/^(.{5})(.*)/).slice(1)

We must use .slice(1) here to discard first element of array which is full match.

edited Oct 19, 2022 at 7:54

answered Oct 19, 2022 at 6:40

anubhava

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Comments

boki_bo · Accepted Answer · 2022-10-19 06:40:17Z

-1

You can do it like this

const splitAt = (index, input) => [input.slice(0, index), input.slice(index)]

answered Oct 19, 2022 at 6:40

boki_bo

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