What is uglifyjs

At this point if you click any token in the minified area, the editor on the left will move to the original location of that minified token. When the compressor warns, you'll get a flashing button in the toolbar. Click on it to display the warnings temporarily covers the minified area. Click a warning in the list to go to that position in the source. If you have "on-the-fly" and fix warnings, the list will update automatically. Those options are saved in localStorage, they will be remembered the next time you visit this page.

Even Uglify calls itself a minification toolkit. Improve this answer. RegarBoy RegarBoy 2, 17 17 silver badges 40 40 bronze badges. So should we Uglify the JS so that its not copied by anyone? Whats the real purpose of Uglification? AdityaBokade It can be copied by someone, but it won't be in a readable format.

Like for instance variable or function names become single letters So, understanding the real purpose of anything declared will get very complicated.

If the JS file size is too big, it's nearly impossible to understand it unless the entire code is re-written. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? If you pass this option, UglifyJS will require "acorn". Acorn is really fast e. One can simply disable compress to speed up Uglify builds by 3 to 5 times.

Various compress transforms that simplify, rearrange, inline and remove code are known to have an adverse effect on debugging with source maps. This is expected as code is optimized and mappings are often simply not possible as some code no longer exists. For highest fidelity in source map debugging disable the Uglify compress option and just use mangle. Skip to content. Star View license. Branches Tags. Could not load branches.

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For more exotic parts of ECMAScript, process your source file with transpilers like Babel before passing onto uglify-js. Install First make sure you have installed the latest version of node. From NPM for use as a command line app: npm install uglify-js -g. You can use this to insert a comment, for example for licensing information.

This will not be parsed, but the source map will adjust for its presence. By default this works like Google Closure, keeping JSDoc-style comments that contain " license" or " preserve". Specify "inline" if the source map is included within the sources. By default UglifyJS will not try to be v8-proof.

By default UglifyJS will not try to be Safari-proof. If variable q is not used elsewhere, UglifyJS will drop it, but will still keep the Math. The current implementation adds some overhead compression will be slower. Specify "strict" to treat foo.

Enabled by default. Some code runs faster in the Chrome V8 engine if this option is disabled. Does not negatively impact other major browsers. May be set to a positive integer to specify the maximum number of consecutive comma sequences that will be generated.

If this option is set to true then the default sequences limit is Set option to false or 0 to disable. The smallest sequences length is 2. A sequences value of 1 is grandfathered to be equivalent to true and as such means On rare occasions the default sequences limit leads to very slow compress times in which case a value of 20 or less is recommended. Implies toplevel. Example: ["foo", "bar"]. Not recommended to override this setting. Pass an empty string "" to enable, or a non-empty string to set the debug suffix.

The code generator tries to output shortest code possible by default. In case you want beautified output, pass --beautify -b. Optionally you can pass additional arguments that control the code output:. The source map will adjust for this text.

Can be used to insert a comment containing licensing information, for example. If you pass false then whenever possible we will use a newline instead of a semicolon, leading to more readable output of uglified code size before gzip could be smaller; size after gzip insignificantly larger.

It refers to the width of the line text excluding indentation. It doesn't work very well currently, but it does make the code generated by UglifyJS more readable. See for more details. You can pass --comments to retain certain comments in the output.

You can pass --comments all to keep all the comments, or a valid JavaScript regexp to keep only comments that match this regexp. Even though it has " preserve", the comment will be lost because the inner function g which is the AST node to which the comment is attached to is discarded by the compressor as not referenced. The safest comments where to place copyright information or other info that needs to be kept in the output are comments attached to toplevel nodes.

It enables some transformations that might break code logic in certain contrived cases, but should be fine for most code. You might want to try it on your own code, it should reduce the minified size. Here's what happens when this flag is on:. You can use the --define -d switch in order to declare global variables that UglifyJS will assume to be constants unless defined in scope.