Longest Common Subsequence in Javascript

longest-common-subsequence.js

/**
 * Simple Longest Common Subsequence
 */

let initial = "ABCDGH";
let compared = "AEDFHR";
let expected = "This is the string";

function assertEquals(expected, actual)
{
    if (expected === actual) {
        console.log(`Assert that [${expected}] is [${actual}] is true!`)
        return
    }
    console.error(`Assert that [${expected}] is [${actual}] is false!`)
    return;
}

function longestCommonSubsequence(initial, compared)
{
    let memo = [...Array(initial.length)].map(e => Array(compared.length));

    const helper = function (initial, compared, indexOfInitial, indexOfCompared) {
        if (indexOfInitial === initial.length || indexOfCompared === compared.length) {
            return '';
        }

        if (memo[indexOfInitial][indexOfCompared] !== undefined) {
            return memo[indexOfInitial][indexOfCompared];
        }

        if (initial[indexOfInitial] === compared[indexOfCompared]) {
            return (memo[indexOfInitial][indexOfCompared] = initial[indexOfInitial] + helper(initial, compared, indexOfInitial + 1, indexOfCompared + 1));
        }

        const first = helper(initial, compared, indexOfInitial + 1, indexOfCompared)
        const second = helper(initial, compared, indexOfInitial, indexOfCompared + 1);

        if (first.length > second.length) {
            return memo[indexOfInitial][indexOfCompared] = first;
        }
        return memo[indexOfInitial][indexOfCompared] = second;
    }

    return helper(initial, compared, 0, 0);
}
let reg = /([ .,])/g;
console.log(initial.split(reg));

let actual = longestCommonSubsequence(initial.split(reg), compared.split(reg))

assertEquals(expected, actual)