自己实现一个数组的slice方法

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)