IsBlank

IsBlank is a predicate used in programming to indicate that a value has no visible content. In string processing, it typically returns true for values that are null, empty, or consist only of whitespace characters.

Common implementations vary by language. In Java, libraries such as Apache Commons StringUtils define isBlank(CharSequence) to return true if the input is null, empty, or whitespace only. In JavaScript, isBlank is often implemented as value == null || /^\s*$/.test(value), or by using a trim-based check such as value == null || value.trim().length === 0. In Kotlin, there is a standard extension isNullOrBlank() for nullable CharSequence, which returns true if the string is null or consists solely of whitespace. In C#, String.IsNullOrWhiteSpace serves a similar purpose, treating null and any amount of whitespace as blank. Python lacks a standard isBlank function; common checks use strip() or isspace on strings.

Edge cases include Unicode whitespace, non-breaking spaces, and locale-specific characters. Some libraries distinguish isBlank from isEmpty: isEmpty usually means the length is zero and does not consider whitespace; isBlank commonly includes whitespace and, in some contexts, null.

Common uses include input validation, data Cleaning, and preprocessing before storage or comparison. See also related predicates such as isEmpty and language-specific equivalents like isNullOrWhiteSpace or isBlank in various standard libraries.