ajaxorg/ace

Ace is a standalone code editor that runs inside a web browser, written in JavaScript. You can embed it into any website or web app and give users a full code-editing experience without requiring any external software installation. The problem it solves: standard HTML text areas are basic input boxes with no code intelligence. Ace brings a proper editor into the browser, comparable to desktop text editors, with syntax highlighting (color-coding) for over 120 programming languages, more than 20 visual themes, automatic indentation, code folding (collapsing sections of code), support for multiple cursors, and search-and-replace using regular expressions. It can handle very large files (the README notes 4,000,000 lines as an upper limit). Embedding it in a web page is straightforward: you include the script file and call a single function pointing at a div element on your page, and that div becomes an interactive code editor. You can then switch the language mode (to activate the right syntax highlighting), set a theme, and configure key bindings including vim and Emacs modes. You'd use Ace when building any web application that needs users to write or edit code directly in the browser, an online coding environment, a configuration editor, a template builder, or similar tool. It's a JavaScript library with no runtime dependencies, distributed via npm (Node.js's package manager), and licensed under BSD.