Question 361753 in Javascript Question posted in
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Javascript – Regex to limit numbers between 0 and 100, and with up to 2 decimals

I’m unable to do or find a regex that allows me to insert in an input numbers between 0 and 100, and also allow to insert up to 2 decimals.

I can have them for separated but can’t merge them. I’m starting to think that there is an inconsistence

  const VALIDATION = {
    ONLY_NUMS: (value: string) => /^[0-9]*$/.test(value),
    BETWEEN_0_AND_100: (value: string) => /^(d{0,2}([.,]d{1,2})?|100([.,]0{1,2})?)$/.test(value),
    FLOAT_NUMS: (value: string) => /^-?[0-9]*((?<=d).(?=d))?[0-9]*$/.test(value) && value !== '-',
  };
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2

Answers


  1. 0

    If your validation logic is already a function, you can parse the string using a leading +n or calling Number(n) to coerce the string into an number.

    Now that it’s a number, you can check if it’s !NaN and in the range.

    const INT_EXPR = /^-?[0-9]+$/;
const FLOAT_EXPR = /^[+-]?([0-9]*[.])?[0-9]+$/;

const inRange = (n: Number, min: Number, max: Number): Boolean => n >= min && n <= max;

const Validation = {
  IS_INTEGER: (value: string) => INT_EXPR.test(value),
  BETWEEN_0_AND_100: (value: string) => !isNaN(+value) && inRange(+value, 0, 100),
  IS_FLOAT: (value: string) => FLOAT_EXPR.test(value),
} as const;

const validCases = [
  Validation.IS_INTEGER('42'),
  Validation.IS_INTEGER('-32'),
  Validation.BETWEEN_0_AND_100('2'),
  Validation.IS_FLOAT('2'),
  Validation.IS_FLOAT('2.01'),
];

const invalidCases = [
  Validation.IS_INTEGER('-'),
  Validation.IS_INTEGER('3.14'),
  Validation.BETWEEN_0_AND_100('-1'),
  Validation.BETWEEN_0_AND_100('101'),
  Validation.IS_FLOAT('-'),
  Validation.IS_FLOAT('A'),
];

// Validate all
function identity<TObj>(obj: TObj): TObj {
  return obj;
}

console.log(validCases.every(identity) && !invalidCases.some(identity));

    Compiled snippet

    const INT_EXPR = /^-?[0-9]+$/;
const FLOAT_EXPR = /^[+-]?([0-9]*[.])?[0-9]+$/;

const inRange = (n, min, max) => n >= min && n <= max;

const Validation = {
    IS_INTEGER: (value) => INT_EXPR.test(value),
    BETWEEN_0_AND_100: (value) => !isNaN(+value) && inRange(+value, 0, 100),
    IS_FLOAT: (value) => FLOAT_EXPR.test(value),
};

const validCases = [
    Validation.IS_INTEGER('42'),
    Validation.IS_INTEGER('-32'),
    Validation.BETWEEN_0_AND_100('2'),
    Validation.IS_FLOAT('2'),
    Validation.IS_FLOAT('2.01'),
];

const invalidCases = [
    Validation.IS_INTEGER('-'),
    Validation.IS_INTEGER('3.14'),
    Validation.BETWEEN_0_AND_100('-1'),
    Validation.BETWEEN_0_AND_100('101'),
    Validation.IS_FLOAT('-'),
    Validation.IS_FLOAT('A'),
];

// Validate all
function identity(obj) {
    return obj;
}

console.log(validCases.every(identity) && !invalidCases.some(identity));
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  2. 0

    If you truly can’t avoid to use regexp, this one should do the trick:

    (^0|^[1-9][0-9]?|^100)($|(.|,)[0-9][0-9]?$)

    It allows even decimal after 100 (like 100.34)
    The below one is up to 100 with no decimal allowed after (max 99.99):

    (^100$|^0|^[1-9][0-9]?)($|(.|,)[0-9][0-9]?$)
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