Function to compare 2 string by percentage.

similarity.js

/**
 * Function to compare 2 string by percentage.
 * 
 * @see https://stackoverflow.com/a/36566052/1427748
 * @param {string} s1 
 * @param {string} s2 
 */
const similarity = (s1, s2) => {
    function editDistance(s1, s2) {
        s1 = s1.toLowerCase();
        s2 = s2.toLowerCase();

        var costs = new Array();
        for (var i = 0; i <= s1.length; i++) {
            var lastValue = i;
            for (var j = 0; j <= s2.length; j++) {
                if (i == 0)
                    costs[j] = j;
                else {
                    if (j > 0) {
                        var newValue = costs[j - 1];
                        if (s1.charAt(i - 1) != s2.charAt(j - 1))
                            newValue = Math.min(Math.min(newValue, lastValue),
                                costs[j]) + 1;
                        costs[j - 1] = lastValue;
                        lastValue = newValue;
                    }
                }
            }
            if (i > 0)
                costs[s2.length] = lastValue;
        }
        return costs[s2.length];
    }

    var longer = s1;
    var shorter = s2;
    if (s1.length < s2.length) {
        longer = s2;
        shorter = s1;
    }
    var longerLength = longer.length;
    if (longerLength == 0) {
        return 1.0;
    }
    return (longerLength - editDistance(longer, shorter)) / parseFloat(longerLength);
}

Great script! I used it to match names between 2 lists, credited you for the find in the Readme and in the function definition.
https://github.com/maskSnorkelFins/listCompare