UglifyJS uses mas to chain function, object and variable declarations. This is fine for productions and when the file is being minified however it makes it extremely hard to walk through the javascript with breakpoints when debugging js. I need to know how to turn this feature off in the UglifyJS Grunt Plugin.

Below is what the output looks like.

var boom = function(a) {
  ...
},
bing = function(b){
  ...
},
bam = function(c) {
  ...
};

UglifyJS uses mas to chain function, object and variable declarations. This is fine for productions and when the file is being minified however it makes it extremely hard to walk through the javascript with breakpoints when debugging js. I need to know how to turn this feature off in the UglifyJS Grunt Plugin.

Below is what the output looks like.

var boom = function(a) {
  ...
},
bing = function(b){
  ...
},
bam = function(c) {
  ...
};

• javascript
• gruntjs
• uglifyjs

• If you have sourcemaps all the way why would you need to put breakpoints into uglified code? – Yury Tarabanko Commented Aug 28, 2014 at 6:12
• 1 To walk the javascript. I've got a pretty plex data modal going on. – etoxin Commented Aug 28, 2014 at 6:13
• 1 Also it's just nice see how your javascript runs with breakpoints. No need for console.logs or debugger statements. I find it a lot neater. – etoxin Commented Aug 28, 2014 at 6:20
• 1 I found the option for UglifyJS now to figure out how to make it work with Grunt. github./mishoo/UglifyJS2#pressor-options – etoxin Commented Aug 28, 2014 at 6:30
• 1 I have sourcemaps. Also it's good practice to setup the entire grunt build process first rather than just before going live. – etoxin Commented Aug 28, 2014 at 12:16

3 Answers 3

This might help Gulp users using gulp-uglify :

  .pipe( uglify({
    press:{
      sequences:false
    }
  }) )

Ok I figured it out. In the the Gruntfile under options > press add an option

sequences: false

that will stop the semi-colons being replaced with mas. You can then use breakpoints like you would normally.

uglify: {
    options: {
        press: {
            sequences: false
        }
    }
}

This might help users of HTML Minifier which uses UglifyJS under the hood:

const htmlmin = require('gulp-html-minifier-terser'); // new fork of gulp-htmlmin

.pipe(htmlmin({
    collapseWhitespace: true,       // etc.
    minifyJS: {press:{sequences:false}}, 
});

I found you can pass through Uglify options via the minifyJS instead of just true which uses all the defaults.