第三天：1000变为1,000
<h5>每三位转为逗号</h5>
<h5>解题思路：字符串和字符串数组</h5>
<pre><code class="language-javascript"> function threeNum(num) {
var num = (num || 0).toString();
var result = '';
while (num.length > 3) {
result = ',' + num.slice(-3) + result; //加入逗号
num = num.slice(0, num.length - 3);
}
if (num) {
result = num + result; //把前面的一位数加上
}
return result;
}
}
console.log(threeNum(10)) //"10"
console.log(threeNum(1000)) //"1,000"</code></pre>