locutus/php/strings/similar_text.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.similar_text = similar_text;
function similar_text(first, second, percent) {
    //      discuss at: https://locutus.io/php/similar_text/
    // parity verified: PHP 8.3
    //     original by: Rafał Kukawski (https://blog.kukawski.pl)
    //     bugfixed by: Chris McMacken
    //     bugfixed by: Jarkko Rantavuori original by findings in stackoverflow (https://stackoverflow.com/questions/14136349/how-does-similar-text-work)
    //     improved by: Markus Padourek (taken from https://www.kevinhq.com/2012/06/php-similartext-function-in-javascript_16.html)
    //       example 1: similar_text('Hello World!', 'Hello locutus!')
    //       returns 1: 8
    //       example 2: similar_text('Hello World!', null)
    //       returns 2: 0
    if (first === null || second === null || typeof first === 'undefined' || typeof second === 'undefined') {
        return 0;
    }
    const firstValue = String(first);
    const secondValue = String(second);
    let pos1 = 0;
    let pos2 = 0;
    let max = 0;
    const firstLength = firstValue.length;
    const secondLength = secondValue.length;
    let sum = 0;
    for (let p = 0; p < firstLength; p++) {
        for (let q = 0; q < secondLength; q++) {
            let l = 0;
            for (l = 0; p + l < firstLength && q + l < secondLength && firstValue.charAt(p + l) === secondValue.charAt(q + l); l++) {
                // @todo: ^-- break up this crazy for loop and put the logic in its body
            }
            if (l > max) {
                max = l;
                pos1 = p;
                pos2 = q;
            }
        }
    }
    sum = max;
    if (sum) {
        if (pos1 && pos2) {
            sum += similar_text(firstValue.substr(0, pos1), secondValue.substr(0, pos2));
        }
        if (pos1 + max < firstLength && pos2 + max < secondLength) {
            sum += similar_text(firstValue.substr(pos1 + max, firstLength - pos1 - max), secondValue.substr(pos2 + max, secondLength - pos2 - max));
        }
    }
    if (!percent) {
        return sum;
    }
    return (sum * 200) / (firstLength + secondLength);
}