js 文本相似度

function similar(s, t, f) {
    if (!s || !t) {
        return 0
    }
    var l = s.length > t.length ? s.length : t.length
    var n = s.length
    var m = t.length
    var d = []
    f = f || 3
    var min = function(a, b, c) {
        return a < b ? (a < c ? a : c) : (b < c ? b : c)
    }
    var i, j, si, tj, cost
    if (n === 0) return m
    if (m === 0) return n
    for (i = 0; i <= n; i++) {
        d[i] = []
        d[i][0] = i
    }
    for (j = 0; j <= m; j++) {
        d[0][j] = j
    }
    for (i = 1; i <= n; i++) {
        si = s.charAt(i - 1)
        for (j = 1; j <= m; j++) {
            tj = t.charAt(j - 1)
            if (si === tj) {
                cost = 0
            } else {
                cost = 1
            }
            d[i][j] = min(d[i - 1][j] + 1, d[i][j - 1] + 1, d[i - 1][j - 1] + cost)
        }
    }
    let res = (1 - d[n][m] / l)
    return res.toFixed(f)
}
 
var s1 = similar('龍鳳店','龍鳳店')  // 1
var s2 = similar('龍_神話與幻獸','龍鳳店')  // 0.1
 
var s1 = similar('龍_神話與幻獸','龍鳳店')  // 0.1
var s2 = similar('龍','龍_神話與幻獸')  // 0.1
 
var s1 = similar('黑豹','龍')  // 0
var s2 = similar('黑豹','黑豹')  // 1
 
var s1 = similar('黑衣人3','黑豹');  // 0.2
var s2 = similar('黑衣人3','黑衣人3');  // 1