A character range from an uppercase to a lowercase should not be used in a regular expression

• BAD_RANGE_IN_CHARACTER_CLASS
• Error
• Medium
• No tags

This rule applies when a character range in a regular expression is from an uppercase letter to a lowercase one.

The ASCII character table has several non-alphabetical characters between the A-Z and a-z ranges. For example, a character range [A-z] is equivalent to [A-Z[\\\]^_`a-z].

Usually, the lowercase letter is a typo because those non-alphabetical characters are unlikely to be intended.
When the characters are actually intended, it is recommended to write them explicitly for code readability.

Noncompliant Code Example

function isAlphaNumeric(str) {
    return /^[0-9A-z]+$/.test(str); // BAD_RANGE_IN_CHARACTER_CLASS alarm
}

Compliant Code Example

function isAlphaNumeric(str) {
    return /^[0-9A-Za-z]+$/.test(str);
}

Version

This rule was introduced in DeepScan 1.26.0.

See

• Regular Expressions

• Groups And Ranges