Extra Backslash Added in Uglifyjs Output of Regex

[ScottHaney]

Summary

When running a certain regex through gulp-uglify on my linux build container an extra backslash is added. A separate build from another machine does not include the extra backslash and so the hashes of the outputted files aren't matching.

I created a docker container that reproduces the issue using gulp-uglify since that is where I first posted this question before being redirected to this repo. The code to build the docker image can be found here and uses gulp-uglify to create the issue although I am also able to create the issue inside the container using uglifyjs after installing uglify-js globally from npm.

Uglify version (uglifyjs -V) : 3.0.4

JavaScript input

function boomBaby(s) { return s.split(/[\\/]/); };

The uglifyjs CLI command executed or minify() options used.

uglifyjs called without options on a file with the input javascript listed above

JavaScript output or error produced.

function boomBaby(s){return s.split(/[\\\/]/)}

[kzc]

Cannot reproduce:

$ bin/uglifyjs -V
3.0.4

$ cat test.js
function boomBaby(s) { return s.split(/[\\/]/); }

$ bin/uglifyjs test.js
function boomBaby(s){return s.split(/[\\/]/)}

[alexlamsl]

@kzc that's weird - I can reproduce this:

> type test.js
function boomBaby(s) { return s.split(/[\\/]/); };
> uglify-js test.js
function boomBaby(s){return s.split(/[\\\/]/)}

Obviously I'm on Windows, though I doubt that makes a difference.

[kzc]

The regexes are equivalent in any event.

It's odd that Windows is different. Are you using Chakra?

[kzc]

Uglify makes no attempt to format RegExp patterns. It relies on the toString() method of the engine.

[kzc]

Duplicate of #885

[alexlamsl]

Just vanilla Node.js:

> nvs use node
PATH = node\7.10.0\x64

> echo function boomBaby(s) { return s.split(/[\\/]/); }; | node bin\uglifyjs
function boomBaby(s){return s.split(/[\\\/]/)}

[alexlamsl]

Ah ha... 🙈

> nvs use node/6
PATH = node\6.10.3\x64

> echo function boomBaby(s) { return s.split(/[\\/]/); }; | node bin\uglifyjs
function boomBaby(s){return s.split(/[\\/]/)}

[kzc]

Yet another reason not to use node 7.

Anyway, nothing actionable here. We're not going to make a regex parser and formatter.

[alexlamsl]

For extra reading: https://github.com/eslint/eslint/blob/master/lib/rules/no-useless-escape.js

But yeah, this isn't uglify-regex so I guess we'll have to leave it as is.

[ScottHaney]

Thank you so much for your prompt and detailed help! This fixed my issue!!