有没有一个更严格的内置javascript函数可以告诉我输入的字符串是否是数字？例如：

// for both of the following it should produce a non-value (nan or undefined or whatever)
> parseFloat('2xa');
2
> parseInt('1ddd')
1

现在我使用正则表达式来实现：

const test_values = [
  // [value, expected]
  ['2.4', 2.4],
  ['1e2', 1e2],
  ['1f', null],
  ['0.28', 0.28],
  ['1e+7', 1e+7],
  ['1e+7.1', null]
]
for (let [val, expected] of test_values) {
  let m = val.match(/^(-?\d*(\.\d+)|\d+)([eE][+-]?\d*)?$/);
  let res = m? parseFloat(m[0]) : null;
  console.log(res === expected? 'OK' : 'ERROR', res);
}