Regex in JavaScript for validating decimal numbers

I want a regex in JavaScript for validating decimal numbers.

It should allow only up to two decimal places. For example, it should allow 10.89 but not 10.899.

It should also allow only one period (.). For example, it should allow 10.89 but not 10.8.9.

Solution 1:

Try the following expression: ^\d+\.\d{0,2}$ If you want the decimal places to be optional, you can use the following: ^\d+(\.\d{1,2})?$

EDIT: To test a string match in Javascript use the following snippet:

var regexp = /^\d+\.\d{0,2}$/;

// returns true
regexp.test('10.5')

Solution 2:

Regex

/^\d+(\.\d{1,2})?$/

Demo

var regexp = /^\d+(\.\d{1,2})?$/;

console.log("'.74' returns " + regexp.test('.74'));
console.log("'7' returns " + regexp.test('7'));
console.log("'10.5' returns " + regexp.test('10.5'));
console.log("'115.25' returns " + regexp.test('115.25'));
console.log("'1535.803' returns " + regexp.test('1535.803'));
console.log("'153.14.5' returns " + regexp.test('153.14.5'));
console.log("'415351108140' returns " + regexp.test('415351108140'));
console.log("'415351108140.5' returns " + regexp.test('415351108140.5'));
console.log("'415351108140.55' returns " + regexp.test('415351108140.55'));
console.log("'415351108140.556' returns " + regexp.test('415351108140.556'));

Explanation

1. / / : the beginning and end of the expression
2. ^ : whatever follows should be at the beginning of the string you're testing
3. \d+ : there should be at least one digit
4. ( )? : this part is optional
5. \. : here goes a dot
6. \d{1,2} : there should be between one and two digits here
7. $ : whatever precedes this should be at the end of the string you're testing

Tip

You can use regexr.com or regex101.com for testing regular expressions directly in the browser!