Regular expression in JavaScript that specifically matches numbers formatted in the style of JavaScript

My goal is to develop a javascript regular expression that specifically identifies valid Javascript-style numbers. The requirements entail accommodating an optional minus or plus sign before the number, recognizing the decimal dot, and supporting exponent notations such as 1e-4 or 1E4, with an additional option for a sign in front of the exponent if necessary.

The pattern should allow digits before or after the dot, but it should not match just a standalone dot. Examples like .2 and 2. should be considered valid, whereas only the dot should not be accepted.

The ideal scenario is to encapsulate the expression within /^...$/; format.

I've managed to cover some aspects, but I aim for my expression to successfully validate common javascript values like .5, -.5, or +5

function validNumber(number) {
    var regexNum = /^-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?$/; 
    return regexNum.test(number);
}

console.log(validNumber("0.0001")); // true
console.log(validNumber("-5")); // true
console.log(validNumber("0.3425")); // true
console.log(validNumber("1e-4")); // true
console.log(validNumber("1E-4")); // true
console.log(validNumber("1Ee-4")); // false
console.log(validNumber("-4.34")); // true
console.log(validNumber("Test123")); // false
console.log(validNumber("+-2")); // false
console.log(validNumber("5.")); // true
console.log(validNumber(".")); // false
console.log(validNumber(".5")); // Should be true, but passes as false
console.log(validNumber("-.5")); // Should be true, but passes as false
console.log(validNumber("+5"));  // Should be true, but passes as false

Do you have any recommendations for this?

Answer №1

Make sure to utilize

/^[-+]?(?:\.[0-9]+|[0-9]+(?:\.[0-9]*)?)(?:[eE][-+]?[0-9]+)?$/

Check out the regex demo

Specifics

  • ^ - beginning of string
  • [-+]? - an optional + or - sign
  • (?:\.[0-9]+|[0-9]+(?:\.[0-9]*)?) - either one of these two sequences:
    • \.[0-9]+ - a period and 1 or more digits
    • | - or
    • [0-9]+(?:\.[0-9]*)? - 1 or more digits, then an optional sequence of a period followed by 0 or more digits
  • (?:[eE][-+]?[0-9]+)? - an optional exponent part:
    • [eE] - an e or E
    • [-+]? - an optional plus or minus sign
    • [0-9]+ - 1 or more digits
  • $ - end of string.

var regexNum = /^[-+]?(?:\.[0-9]+|[0-9]+(?:\.[0-9]*)?)(?:[eE][-+]?[0-9]+)?$/;

function validateNumber(num) {
    return regexNum.test(num);
}

console.log("0.0001", validateNumber("0.0001")); // true
console.log("-5", validateNumber("-5")); // true
console.log("0.3425", validateNumber("0.3425")); // true
console.log("1e-4", validateNumber("1e-4")); // true
console.log("1E-4", validateNumber("1E-4")); // true
console.log("1Ee-4", validateNumber("1Ee-4")); // false
console.log("-4.34", validateNumber("-4.34")); // true
console.log("Test123", validateNumber("Test123")); // false
console.log("+-2", validateNumber("+-2")); // false
console.log("5.", validateNumber("5.")); // true
console.log(".", validateNumber(".")); // false
console.log(".5", validateNumber(".5")); // Should be true, but is registering as false
console.log("-.5", validateNumber("-.5")); // Should be true, but is registering as false
console.log("+5", validateNumber("+5"));  

Answer №2

Could you verify the following regular expression?

const regexPattern = new RegExp("(^([-|+]?)([0-9]{0,12}?)(\.)([0-9]){0,12}$)|(^([-|+]?)([0-9]){0,12}$)");

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