similarityOfStrings.js

export default function similarityOfStrings(s1, s2) {
    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);
}

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];
}