replacer

A replacer is a tool or component that substitutes specified input strings or tokens with designated replacements. Replacers are used to modify text, transform data, or generate output from templates.

In computing, replacers enable find-and-replace operations, string manipulation, and data normalization. They come in simple literal forms that substitute exact strings and in more advanced forms that use regular expressions.

Common implementations include text editors and word processors, command-line tools such as sed or Perl, programming language libraries (for example, Python's str.replace and re.sub, JavaScript's replace), and templating engines that substitute placeholders with values.

Replacer behavior can be single-pass or streaming, global or limited to the first occurrence, and case-sensitive or insensitive. Important considerations include escaping, handling overlapping matches, performance on large inputs, and ensuring replacements do not introduce unwanted side effects.

Use cases include data cleaning, template rendering, configuration management, and batch renaming of files or content. See also find and replace, templating, and regex.