Please upgrade uglify-js & uglify-es

[ZekeXu]

Node v10.5.0
Npm 6.4.1
uglifyjs-webpack-plugin 1.3.0

Now will compile

const dropdownView = Object(_ckeditor_ckeditor5_ui_src_dropdown_utils__WEBPACK_IMPORTED_MODULE_7__["createDropdown"])( locale, _ckeditor_ckeditor5_ui_src_dropdown_button_splitbuttonview__WEBPACK_IMPORTED_MODULE_6__["default"] );

...

const actionView = dropdownView.buttonView.actionView;
actionView.iconView.bind( 'fillColor' ).to( dropdownView.buttonView, 'color' );

to

(c = c).buttonView.actionView.iconView.bind("fillColor").to(c.buttonView, "color"),

Maybe upgrade could solve this.

[alexander-akait]

@ZekeXu please use https://github.com/webpack-contrib/terser-webpack-plugin, uglify-es is abadoned and next version of plugin will use uglify-js (doesn't support es6)