KMP algorithm for substring search

KMP-substring-search.js

/**
 * @param {string} haystack
 * @param {string} needle
 * @return {number}
 */
function KMP(text, pattern){
	let LPS = preProcess(pattern);
	let i=0, j=0;
	while(i < text.length && j < pattern.length){
		if(text[i] == pattern[j]){
			i++;
			j++;
		} else if(j!=0){
			j = LPS[j-1];
		} else {
			i++;
		}
	}
	if(j == pattern.length){
		return true; // if you want to return the position, then (i - j )
	}
    return false;
}