Question

I would very much appreciate some assistance from the community on replacing a string at xth position intervals, using javascript regex. For example, if the string length is 161 and the replacement text is <br />, regex would replace the string at the 40th, 80th, 120th, and 160th positions with this replacement text. Is this possible using regex?

Thank you very much.

Answer 1

A method to add <br /> at ever 40th position is by using the following line:

string = string.replace(/([\S\s]{40})/g , "$1<br />");

If you want to dynamically set the position use:

var positions = 40;
var pattern = new RegExp("([\\s\\s]{" + positions + "})", "g");
string = string.replace(pattern , "$1<br />");

Explanation of the code:

1. The first argument of the replace function is a RegExp:
   • ([\S\s] = all non-whitespace and white-space characters = every character).
   • {40} = 40 characters
   • The g flag means: global match, ie: match every possible occurence
   • The parentheses inside the RegExp means: Create a group. This group can later be referred by $1 (first group)
2. The second argument of the replace function contains $1<br />. That is: replace the full match by the first group ($1), and add <br /> to it.