minification (programming)
{{short description|Removal of unnecessary characters in code without changing its functionality}}
{{other uses|Minimisation (disambiguation){{!}}Minimisation}}
{{Redirect|Terser|the basic topic|terseness}}
{{Use dmy dates|date=September 2021}}
Minification (also minimisation or minimization) is the process of removing all unnecessary characters from the source code of interpreted programming languages or markup languages without changing its functionality. These unnecessary characters usually include whitespace characters, new line characters, comments, and sometimes block delimiters, which are used to add readability to the code but are not required for it to execute. Minification reduces the size of the source code, making its transmission over a network (e.g. the Internet) more efficient. In programmer culture, aiming at extremely minified source code is the purpose of recreational code golf competitions and a part of the demoscene.
Minification can be distinguished from the more general concept of data compression in that the minified source can be interpreted immediately without the need for a decompression step: the same interpreter can work with both the original as well as with the minified source.
The goals of minification are not the same as the goals of obfuscation; the former is often intended to be reversed using a pretty-printer{{citation needed|date=July 2020}} or unminifier. However, to achieve its goals, minification sometimes uses techniques also used by obfuscation; for example, shortening variable names and refactoring the source code. When minification uses such techniques, the pretty-printer or unminifier can only fully reverse the minification process if it is supplied details of the transformations done by such techniques. If not supplied those details, the reversed source code will contain different variable names and control flow, even though it will have the same functionality as the original source code.
Example
For example, the JavaScript code
// This is a comment that will be removed by the minifier
var array = [];
for (var i = 0; i < 20; i++) {
array[i] = i;
}
is equivalent to but longer than
for(var a=[],i=0;i<20;a[i]=i++);
History
In 2001 Douglas Crockford introduced JSMin,{{Cite web |title=JSMin: The JavaScript Minifier |url=https://www.crockford.com/javascript/jsmin.html |website=Crockford.com |date=11 September 2001 |first=Douglas |last=Crockford |publisher=Self-published|archive-url=https://web.archive.org/web/20020405140416/https://www.crockford.com/javascript/jsmin.html |archive-date=5 April 2002 }} which removed comments and whitespace from JavaScript code.{{Cite web |url = https://webplatform.github.io/docs/concepts/programming/javascript/minification/ |title = Code minification |website = webplatform.github.io |publisher=The WebPlatform Project |url-status = live |archive-url = https://web.archive.org/web/20160424125048/https://docs.webplatform.org/wiki/concepts/programming/javascript/minification |archive-date = 24 April 2016}} It was followed by YUI Compressor in 2007. In 2009, Google opened up its Closure toolkit, including Closure Compiler which contained a source mapping feature together with a Firefox extension called Closure Inspector.{{Cite web |url=https://arstechnica.com/information-technology/2009/11/google-opens-up-its-javascript-development-toolbox-to-all/ |title=Google opens up its JavaScript development toolbox to all |website=Ars Technica |first=Ryan |last=Paul |date=6 November 2009}} In 2010, Mihai Bazon introduced UglifyJS, which was superseded by UglifyJS2 in 2012; the rewrite was to allow for source map support.{{Cite web |url=http://lisperator.net/blog/should-you-switch-to-uglifyjs2/ |title=Should you switch to UglifyJS2? |last=Bazon |first=Mihai |website=lisperator.net |date=8 November 2012 |publisher=Self-published}} From 2017, Alex Lam took over maintenance and development of UglifyJS2, replacing it with UglifyJS3 which unified the CLI with the API.{{Cite web |url=https://www.npmjs.com/package/uglify-js/v/3.0.0 |title=uglify-js NPM |website=npmjs.com |date=6 May 2017 }} In 2018, Terser has been forked from uglify-es{{Cite web |title=terser · JavaScript mangler and compressor toolkit for ES6+ |url=https://terser.org/ |access-date=2023-01-29 |website=terser.org}}https://github.com//terser/commit/3ef6879ecafd12b57e575ec85e6104e71d5a1b6f {{dead link|date=January 2024}} and has gained momentum since; in 2020 it outstripped UglifyJS when measured in daily downloads.{{cite web | url=https://npmtrends.com/terser-vs-uglify-js | title=Terser vs uglify-js |website= NPM trends |url-status=live |archive-url=https://archive.today/20240127214344/https://npmtrends.com/terser-vs-uglify-js |archive-date= 27 January 2024}}
Source mapping
A source map is a file format that allows software tools for JavaScript to display different code to a user than the code actually executed by the computer. For example, to aid in debugging of minified code, by "mapping" this code to the original unminified source code instead.
The original format was created by Joseph Schorr as part of the Closure Inspector minification project.{{Cite web|date=2011-01-11|title=Source Map Revision 3 Proposal|url=https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit|url-status=dead|archive-url=https://web.archive.org/web/20160308081352/https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit|archive-date=8 March 2016|access-date=2016-04-16}} Version 2 and 3 of the format reduced the size of the map files considerably.
Types
=Tools=
Visual Studio Code comes with minification support for several languages. It can readily browse the Visual Studio Marketplace to download and install additional minifiers.
JavaScript optimizers can minify and generate source maps. In addition certain online tools can compress CSS files.{{Cite web |last=Megida |first=Dillion |date=2022-05-18 |title=Minify CSS – CSS Minifying and Compression Explained |url=https://www.freecodecamp.org/news/minify-css-css-minifying-and-compression-explained/#howtominifycss |access-date=2024-03-29 |website=Free Code Camp |language=en}}
=Web development=
Components and libraries for Web applications and websites have been developed to optimize file requests and reduce page load times by shrinking the size of various files.
JavaScript and Cascading Style Sheets (CSS) resources may be minified, preserving their behavior while considerably reducing their file size. Libraries available online are capable of minification and optimization to varying degrees. Some libraries also merge multiple script files into a single file for client download. JavaScript source maps can make code readable and debuggable even after it has been combined and minified.{{Cite web |last=Seddon |first=Ryan |date=March 21, 2012 |title=Introduction to JavaScript Source Maps |url=http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/ |url-status=dead |archive-url=https://web.archive.org/web/20211228111603/http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/ |archive-date=Dec 28, 2021 |website=HTML5 Rocks}}