javascript 判断是否为数字
 

function isNumberTest(str) {
  const method1 = (v) => {
    let exp = /^[+-]?\d*(\.\d*)?(e[+-]?\d+)?$/;
    // exp.test("+1.9"); // true
    // exp.test("-.1e11"); // true
    return exp.test(v) && str !== "";
  };
  const method2 = (v) => {
    return !isNaN(parseFloat(v)) && isFinite(v);
  };
  // const test = () => {
  //   console.log("null", isNumberTest(null));
  //   console.log("undefined", isNumberTest(undefined));
  //   console.log("NaN", isNumberTest(parseInt("a")));
  //   console.log("empty string", isNumberTest(""));
  //   console.log("123", isNumberTest("123"));
  //   console.log("123abc", isNumberTest("123abc"));
  //   console.log("0.1", isNumberTest("0.1"));
  //   console.log(0, isNumberTest(0));
  //   console.log(0.1, isNumberTest(0.1));
  //   console.log(-0.1, isNumberTest(-0.1));
  // };
  return method1(str);
}