The simplest way to find the number of times a character is repeated in a string in javascript is to iterate over the string and find all the character occurrences.
Example
let s = "hello world!"; let searchChar = "l"; let count = 0; for(let i = 0; i < s.length; i ++) { if(s[i] == searchChar) { count ++; } } console.log(count)
Output
3