Determining whether strings are whole numbers js

1. There may also be a decimal point

var test = ['123.12', '.123', '123.', '123a'];
var reg = /^[\d|\.]*$/;
test.forEach((v) => {
  console.log(v, reg.test(v));
});

2. In addition to the regular, isNaN perhaps better

var test = ['123.12', '.123', '123.', '123a', '1e+43'];

test.forEach((v) => {
  console.log(v, !isNaN(v));
});

 Do not use direct isNaN()

function isNumber(value) {
  return !Number.isNaN(Number(value))
}

 3. For a given digital representation of various types (mainly contains an integer, positive or negative decimal number, and the corresponding scientific notation represented)

var numbers = [
    123, +123, -123,
    '123', '+123', '-123',
    123.4, +123.4, -123.4,
    '123.4', '+123.4', '-123.4',
    123., +123., -123.,
    '123.', '+123.', '-123.',
    .123,, +.123, -.123,
    '.123', '+.123', '-.123',
    1.23e+20, +1.23e+20, -1.23e+20,
    '1.23e+20', '+1.23e+20', '-1.23e+20',
    '123.4.5',
    '123abc456',
    undefined
];

 3.1, used !isNaNfor judgment.

numbers.forEach((v) => {
  console.log(typeof(v), "\t", v, "\t", !isNaN(v));
});

 result:

number      123      true
number      123      true
number      -123      true
string      123      true
string      +123      true
string      -123      true
number      123.4      true
number      123.4      true
number      -123.4      true
string      123.4      true
string      +123.4      true
string      -123.4      true
number      123      true
number      123      true
number      -123      true
string      123.      true
string      +123.      true
string      -123.      true
number      0.123      true
number      0.123      true
number      -0.123      true
string      .123      true
string      +.123      true
string      -.123      true
number      123000000000000000000      true
number      123000000000000000000      true
number      -123000000000000000000      true
string      1.23e+20      true
string      +1.23e+20      true
string      -1.23e+20      true
string      123.4.5      false
string      123abc456      false
undefined      undefined      false

3.2, using regular expressions to determine: integer without sign

var reg = /^[\d]+$/;
numbers.forEach((v) => {
  console.log(typeof(v), "\t", v, "\t", reg.test(v));
});

The results are as follows:

number      123      true
number      123      true
number      -123      false
string      123      true
string      +123      false
string      -123      false
number      123.4      false
number      123.4      false
number      -123.4      false
string      123.4      false
string      +123.4      false
string      -123.4      false
number      123      true
number      123      true
number      -123      false
string      123.      false
string      +123.      false
string      -123.      false
number      0.123      false
number      0.123      false
number      -0.123      false
string      .123      false
string      +.123      false
string      -.123      false
number      123000000000000000000      true
number      123000000000000000000      true
number      -123000000000000000000      false
string      1.23e+20      false
string      +1.23e+20      false
string      -1.23e+20      false
string      123.4.5      false
string      123abc456      false
undefined      undefined      false

3.3, using regular expressions to determine: integer + + scientific notation of decimal, signed

var reg = /^[\+-]?(\d+\.?\d*|\.\d+|\d\.\d+e\+\d+)$/;
numbers.forEach((v) => {
  console.log(typeof(v), "\t", v, "\t", reg.test(v));
});

The results are as follows:

number      123      true
number      123      true
number      -123      true
string      123      true
string      +123      true
string      -123      true
number      123.4      true
number      123.4      true
number      -123.4      true
string      123.4      true
string      +123.4      true
string      -123.4      true
number      123      true
number      123      true
number      -123      true
string      123.      true
string      +123.      true
string      -123.      true
number      0.123      true
number      0.123      true
number      -0.123      true
string      .123      true
string      +.123      true
string      -.123      true
number      123000000000000000000      true
number      123000000000000000000      true
number      -123000000000000000000      true
string      1.23e+20      true
string      +1.23e+20      true
string      -1.23e+20      true
string      123.4.5      false
string      123abc456      false
undefined      undefined      false