Error in Javascript: Character class range is not in order

Question

Error in Javascript: Character class range is not in order

My regular expression (regex) seems to be incorrect:

var domain = "google\.com\.br";
var reEmail = new RegExp("^([A-Za-z0-9_\-\.])+\@" + domain + "$");

I am trying to use this regex to validate an email address. Here is an example:

reEmail.test("<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="4b2824253f2a283f0b2c24242c272e65282426652939">[email protected]</a>");

However, I keep encountering the following error message:

The range specified in the character class is out of order

javascript regex validation

Answer 1

Answer №1

When you create the RegExp using a String, the characters _\-\. get interpreted as _-., resulting in an invalid range. (This creates a range from _ to ., which is incorrect)

To fix this issue, you must double escape it:

new RegExp("^([A-Za-z0-9_\\-\\.])+@" + domain + "$");

This way, the \\ becomes a \ in the String and correctly escapes the - in the RegExp.

UPDATE:

It's always helpful to log the result when creating a RegExp from a String so you can verify if it's correct:

For example, logging your part of the RegExp would show:

console.log("^([A-Za-z0-9_\-\.])+\@");

Which results in:

^([A-Za-z0-9_-.])+@

Answer 2

When you create the RegExp using a String, the characters _\-\. get interpreted as _-., resulting in an invalid range. (This creates a range from _ to ., which is incorrect)

To fix this issue, you must double escape it:

new RegExp("^([A-Za-z0-9_\\-\\.])+@" + domain + "$");

This way, the \\ becomes a \ in the String and correctly escapes the - in the RegExp.

UPDATE:

It's always helpful to log the result when creating a RegExp from a String so you can verify if it's correct:

For example, logging your part of the RegExp would show:

console.log("^([A-Za-z0-9_\-\.])+\@");

Which results in:

^([A-Za-z0-9_-.])+@

Answer 3

Answer №2

RegEx operates on strings, not numbers, which is why you can't use /[1-16]/ for a 2 digit number range like 1 to 16 - this will result in an error as it is not a valid range.

To properly define the range, you should use:

/([1-9]|1[0-6])/;

It's important to note that when using the above expression, you must also specify that the value should be less than 17 to avoid unintended matches with numbers containing 6 like 26 or 36.

Alternatively, you can use the following approach:

/1|2|3...|15|16/

In the second method, you need to replace the ellipsis (...) with |4|5 and so forth.

For more information on REGEX ranges, visit

If needed, consider utilizing a FOR LOOP to filter or test your data instead.

Answer 4

RegEx operates on strings, not numbers, which is why you can't use /[1-16]/ for a 2 digit number range like 1 to 16 - this will result in an error as it is not a valid range.

To properly define the range, you should use:

/([1-9]|1[0-6])/;

It's important to note that when using the above expression, you must also specify that the value should be less than 17 to avoid unintended matches with numbers containing 6 like 26 or 36.

Alternatively, you can use the following approach:

/1|2|3...|15|16/

In the second method, you need to replace the ellipsis (...) with |4|5 and so forth.

For more information on REGEX ranges, visit

If needed, consider utilizing a FOR LOOP to filter or test your data instead.

Error in Javascript: Character class range is not in order

Answer №1

Answer №2

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