[JavaScript]数字取小数点后固定位数

object.toFixed([n])

1. 舍弃规则为<code>四舍五入</code>
2. object必须为数字,若为字符串会报异常<code>Uncaught TypeError: test.toFixed is not a function</code>
   <pre>
   var test = "100";
   test.toFixed(1);
   </pre>
3. 若参数为空,默认位数为0
   <pre>
   var test = "100";
   test = parseInt(test);
   test.toFixed();
   console.log(test);
   </pre>
   结果为:<code>100</code>
4. 参数范围为[0, 20],若超出范围为会报异常<code>Uncaught RangeError: toFixed() digits argument must be between 0 and 20</code>
   <pre>
   var test = "100";
   test = parseInt(test);
   test.toFixed(21);
   console.log(test);
   </pre>