JavaScript ReverseMatch

Question

Is simple, i have this sentence:

str = "aeiou";

Need RegExp to scan string every X chars, but in reverse.

Example:

let every=2,
    match = new RegExp(/>>RegExp Here<</gi);  
//result "a ei ou"

Please post the code that fails to see where the programming issue is. — Wiktor Stribiżew, Mar 13 '20 at 14:47
Why do you need a RegEx here? There are other tools for string parsing/manipulation other than regexes. — gen_Eric, Mar 13 '20 at 14:50
I speak spanish, used translater. Need that RegExp because need format numbers, and *more functions*, but i dont wanna use plugins, only simple javascript — Alejandro Reyes, Mar 13 '20 at 14:58

score 2 · Accepted Answer · answered Mar 13 '20 at 15:05

Use

let str = "Hello world, 13th Mar 2020.";
let every=2;
let rx = new RegExp(`(?=(?:[^]{${every}})+$)`, 'g');
console.log(str.replace(rx, "_"));
// => H_el_lo_ w_or_ld_, _13_th_ M_ar_ 2_02_0.

The regex is /(?=(?:[^]{2})+$)/g, see the regex demo. It matches any location in the string that is followed with one or more repetitions of any two chars up to the string end, and inserts _ at that location.

Details

(?= - start of a positive lookahead:
- (?:[^]{2}) - any char ([^] = [\s\S]), 1 or more times (thanks to +)
- $ - end of string
) - end of the lookahead.

JavaScript ReverseMatch

1 Answers1