Substitute all letters except the first in each word

text = "Lorem Ipsum has been the industry's standard dummy text ever since the 1500s,";

substitute_with = "_";

const regex = '\B[A-Za-z]';
// const regex = '\B\w';
// const regex = '(\w{1})\w*';

var result = text.replaceAll(regex, substitute_with);

I would like to substitute with underscore all letters except the first in each word.

I have failed miserably. Could you help me?

>Solution :

Use the g (global) flag with replace():

const text = "Lorem Ipsum has been the industry's standard dummy text ever since the 1500s,";
const substitute_with = "_";

const regex = /\B[A-Za-z]/g;
var result = text.replace(regex, substitute_with);

console.log(result);

L____ I____ h__ b___ t__ i_______’s s_______ d____ t___ e___ s____ t__ 1500_,

Of course, this can also be done without regex using split(), substring(), repeat() and join():

const result = text.split(' ')
    .map(w => w.substring(0, 1) + substitute_with.repeat(w.length - 1))
    .join(' ');