Boyer Moore string search algorithm implementation in Javascript

Boyer-Moore.js

/**
 * Returns the index of the first occurence of given string in the phrase
 * In case of no match, returns -1
 * 
 * @param text string to be searched 
 * @param pattern string to be found in the text
 */
export function boyerMooreSearch(text: string, pattern: string): number {
    
    // Handle edge case
    if (pattern.length === 0) {
        return -1;
    }

    let charTable = makeCharTable(pattern);
    let offsetTable = makeOffsetTable(pattern);

    for (let i = pattern.length - 1, j; i < text.length;) {
        for (j = pattern.length - 1; pattern[j] == text[i]; i--, j--) {
            if (j === 0) {
                return i;
            }
        }

        const charCode = text.charCodeAt(i);
        i+= Math.max(offsetTable[pattern.length - 1 - j], charTable[charCode]);
    }

    return -1;
}

/**
 * Creates jump table, based on mismatched character information
 */
function makeCharTable(pattern: string): number[] {
    let table = [];

    // 65536 being the max value of char + 1
    for (let i = 0; i < 65536; i++) {
        table.push(pattern.length);
    }

    for (let i = 0; i < pattern.length - 1; i++) {
        const charCode = pattern.charCodeAt(i);
        table[charCode] = pattern.length - 1 - i;
    }

    return table;
}


function makeOffsetTable(pattern: string): number[] {
    let table = [];
    table.length = pattern.length;

    let lastPrefixPosition = pattern.length;

    for (let i = pattern.length; i > 0; i--) {
        if (isPrefix(pattern, i)) {
            lastPrefixPosition = i;
        }

        table[pattern.length - i] = lastPrefixPosition - 1 + pattern.length;
    }

    for (let i = 0; i < pattern.length - 1; i++) {
        const slen = suffixLength(pattern, i);
        table[slen] = pattern.length - 1 - i + slen;
    }

    return table;
}

function isPrefix(pattern: string, p: number): boolean {
    for (let i = p, j = 0; i < pattern.length; i++, j++) {
        if (pattern[i] != pattern[j]) {
            return false;
        }

        return true;
    }
}

function suffixLength(pattern: string, p: number) {
    let len = 0;

    for (let i = p, j = pattern.length - 1; i >= 0 && pattern[i] == pattern[j]; i--, j--) {
        len += 1;
    }

    return len;
}

Hey @Kamilczak020. What license is this code?

I think there's a typo here, shouldn't the return statement in Line 80 be outside the for loop?