js 对比字符串相似度

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)
    },