v2.9.0

• Add JS (ECMAScript 2020) minifier
• Improve benchmark functions
• Predefine byte-slices instead of inline for performance
• Don't check write errors to output during minification, but check at the end only
• Lexers/parser now require passing parse.Input instead of io.Reader
• Rename subpackage min to minify

JS minifier overview

Features:

• remove superfluous whitespace
• remove superfluous semicolons
• shorten true, false, and undefined to !0, !1 and void 0
• rename variables and functions to shorter names (not in global scope)
• move var declarations to the top of the global/function scope (if more than one)
• collapse if/else statements to expressions
• minify conditional expressions to simpler ones
• merge sequential expression statements to one, including into return and throw
• remove superfluous grouping in expressions
• shorten or remove string escapes
• convert object key or index expression from string to identifier or decimal
• merge concatenated strings
• rewrite numbers (binary, octal, decimal, hexadecimal) to shorter representations

It compresses files at about 25 MB/s (only minifying, not considering reading/writing files) which is (much) faster than existing minifiers. Compression rate is between 1.5 and 3.0 depending on the file (respectively, the compression file size is between 35% -- 65% of the original). Example of known files:

File	Original Size	Compressed Size	Ratio	Time	Speed
ace.js	644 kB	346 kB	53.7%	34ms	19 MB/s
dot.js	5.2 kB	3.3 kB	64.9%	563µs	9.2 MB/s
jquery.js	247 kB	85 kB	34.4%	11ms	22 MB/s
jqueryui.js	470 kB	241 kB	51.3%	26ms	18 MB/s
moment.js	99 kB	35 kB	34.9%	4ms	24 MB/s

The minifier has been tested for a number of web applications including WordPress. The go-fuzz fuzzer has been used extensively in order to detect bugs, and will continue finding bugs using https://github.com/google/oss-fuzz