Array.prototype.mySlice = function mySlice() {    var n = arguments[0], m = arguments[1], newAry = [];    n = n === undefined ? 0 : (isNaN(n) ? 0 : (n >= 0 ? (n < this.length ? Math.floor(Number(n)) : this.length) : (n < -this.length ? 0 : (n <= -1 ? this.length + Math.ceil(Number(n)) : 0))));    m = m === undefined ? this.length : (isNaN(m) ? 0 : (m >= 0 ? (m < this.length ? Math.floor(Number(m)) : this.length) : (m < -this.length ? 0 : this.length + Math.ceil(Number(m)))));    while (n < m) {        newAry[newAry.length] = this[n];        n++;    }    return newAry;};

以下是测试代码，和原生的数组slice方法，功能一致。

var ary = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];function compare(n, m) {    console.log(n, m, ary.slice(n, m), 'VS', ary.mySlice(n, m));}compare(0, -5);compare(0, -1.5);compare(-1.5);compare(-0.1);compare(-0.1, 5);compare(0);compare(undefined, "undefined");compare(undefined, undefined);compare("undefined", undefined);compare(100, undefined);compare(-100, undefined);compare(10, undefined);compare(-10, undefined);compare(-10);compare(NaN, NaN);compare(NaN, undefined);compare(undefined, NaN);compare(2, 1);compare(-12, 13);compare(3, 18);compare(0, 0);compare(-200);compare(1, 1);compare(-1, undefined);compare(-1, 1000);compare(2, undefined);compare(123, 123, 123);compare(0, 123);compare(13, undefined)