Is This the Correct Regex for Validating Dates in DD/MM/YYYY Format?

Javascript Regex for Validating Dates in DD/MM/YYYY Format

In this post, we'll explore the regex pattern for validating dates in the DD/MM/YYYY format, specifically for a Spanish-language setting.

The Correct Regex Pattern

The provided regex string, (0[1-9]|[12][0-9]|3[01])[ .-](0[1-9]|1[012])[ .-](19|20|)dd, does not correctly validate dates in DD/MM/YYYY format.

The correct regex pattern for this format is:

^(0?[1-9]|[12][0-9]|3[01])[\/\-](0?[1-9]|1[012])[\/\-]\d{4}$

This pattern flips the day and month components compared to the original YYYY-MM-DD pattern. It also specifies that only the forward slash (/) or hyphen (-) should be used as separators.

Escaping the Slashes

When using the regex pattern in JavaScript code, you need to escape the forward slashes to prevent them from being interpreted as line breaks. This can be done by adding a backslash () before each slash:

const regex = /^(0?[1-9]|[12][0-9]|3[01])[\/\-]^(0?[1-9]|1[012])[\/\-]\d{4}$/

Example Usage

The following JavaScript code demonstrates how to use the regular expression to validate a date in DD/MM/YYYY format:

const testDate = "15/05/2023";
const isValid = testDate.match(regex);

if (isValid) {
  console.log("Valid date.");
} else {
  console.log("Invalid date.");
}

This code would output "Valid date." because "15/05/2023" is a valid date in the DD/MM/YYYY format.

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