Knuth-Morris-Pratt string matcher in TypeScript

kmp.ts

function KMPSearch(pattern: string, text: string): number {
	if (pattern.length === 0) return 0; 

    const lsp = generateLSP(pattern);

	let j = 0; 
	for (let i = 0; i < text.length; i++) {
		while (j > 0 && text.charAt(i) !== pattern.charAt(j)) {
			j = lsp[j - 1];
        }
		if (text.charAt(i) === pattern.charAt(j)) {
			j++;
			if (j === pattern.length) {
				return i - (j - 1);
            }
		}
	}
	return -1;
}

function generateLSP(pattern: string): number[] {
    if (pattern.length === 0) return [];

    let lsp: Array<number> = [0];

	for (let i = 1; i < pattern.length; i++) {
        let c = pattern.charAt(i);
        let j: number = lsp[i - 1];
		while (j > 0 && c !== pattern.charAt(j)) {
			j = lsp[j - 1];
        }

		if (c === pattern.charAt(j)) {
			j++;
        }

        lsp.push(j);
    }

    console.log(lsp);
    return lsp;
}

console.log(KMPSearch("abcdaba", "abcccccdababcdaba"));