The regular expression pattern ((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,} is functional when used on regexpal.com, however, it does not yield the

Question

The regular expression pattern ((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,} is functional when used on regexpal.com, however, it does not yield the

Within the code snippet below, the regular expression in the "pattern" variable is specifically designed to only match the criteria mentioned in the comment (which requires a minimum of 1 letter followed by a dot, and then two letters).

var link = "Help"
// matches www-data.it -- needs at least (1 letter + '.' + 2 letters )
var pattern = '((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}';
var re2 = new RegExp('^' + pattern, 'i');

// if no http and there is something.something
if (link.search(re2) == 0)
{
    link = link;
}

Testing this code on shows successful results as expected, where only strings with the format something.something pass.

However, testing it on JSFiddle and in live production results in unexpected matches such as "Help." http://jsfiddle.net/2jU4D/

This discrepancy raises questions about the functionality of the code. What could be causing this inconsistency?

javascript regex

Answer 1

Answer №1

For creating the regular expression, it is recommended to use native regex syntax:

var re2 = /^((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}/i;

When constructing the regular expression, keep in mind that the \. will appear as just a period . when using new RegExp(). The backslash serves as an escape character in string grammar and may be ignored during initial parsing as a string.

Another approach could be:

var pattern = '((xn--)?[a-z0-9]+(-[a-z0-9]+)*\\.)+[a-z]{2,}';
var re2 = new RegExp('^' + pattern, 'i');

To ensure the correct string is passed to the RegExp constructor, doubling the backslash is necessary.

Answer 2

For creating the regular expression, it is recommended to use native regex syntax:

var re2 = /^((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}/i;

When constructing the regular expression, keep in mind that the \. will appear as just a period . when using new RegExp(). The backslash serves as an escape character in string grammar and may be ignored during initial parsing as a string.

Another approach could be:

var pattern = '((xn--)?[a-z0-9]+(-[a-z0-9]+)*\\.)+[a-z]{2,}';
var re2 = new RegExp('^' + pattern, 'i');

To ensure the correct string is passed to the RegExp constructor, doubling the backslash is necessary.

Answer 3

Answer №2

Below is the analysis of what it corresponds to. I suggest replacing all capture groups with non-capture groups and placing all anchors within the body of a regex (instead of appending them later).

The regex appears to be valid, although there may be some issues with the delimiters or how it is being utilized.
Take note of the necessary components, as there seems to be an issue with the matching process, however, this might not necessarily be due to the regex itself.

(                         # (1 start)
    ( xn-- )?                 # (2), optional capture 'xn--'
    [a-z0-9]+                 # multiple occurrences of lower case letters or digits
    ( - [a-z0-9]+ )*          # (3), optional multiple captures of '-' followed by lower case letters or digits
    \.                        # a dot '.'
)+                        # (1 end), repeat this pattern multiple times
[a-z]{2,}                 # Two or more lower case letters

Answer 4

Below is the analysis of what it corresponds to. I suggest replacing all capture groups with non-capture groups and placing all anchors within the body of a regex (instead of appending them later).

The regex appears to be valid, although there may be some issues with the delimiters or how it is being utilized.
Take note of the necessary components, as there seems to be an issue with the matching process, however, this might not necessarily be due to the regex itself.

(                         # (1 start)
    ( xn-- )?                 # (2), optional capture 'xn--'
    [a-z0-9]+                 # multiple occurrences of lower case letters or digits
    ( - [a-z0-9]+ )*          # (3), optional multiple captures of '-' followed by lower case letters or digits
    \.                        # a dot '.'
)+                        # (1 end), repeat this pattern multiple times
[a-z]{2,}                 # Two or more lower case letters

The regular expression pattern ((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,} is functional when used on regexpal.com, however, it does not yield the

Answer №1

Answer №2

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