command line compiling generates bigger file than the online version - google-closure-compiler

Question

I am testing google closure compiler on command line.
I took the latest version :
java -jar closure-compiler.jar --version
Closure Compiler (http://github.com/google/closure-compiler)
Version: v20190618
Built on: 2019-06-21 17:24
I am generating a compressed version of my javascript like this :
java -jar closure-compiler.jar my_script.js > out.js
The problem is that the generated code is bigger than the one I get when I use the online service at https://closure-compiler.appspot.com/home
I noticed that the command line version added, at the beginning, the following code :
var $jscomp=$jscomp||{};$jscomp.scope={};$jscomp.findInternal=function(a,c,b){a instanceof String&&(a=String(a));for(var d=a.length,e=0;e<d;e++){var f=a[e];if(c.call(b,f,e,a))return{i:e,v:f}}return{i:-1,v:void 0}};$jscomp.ASSUME_ES5=!1;$jscomp.ASSUME_NO_NATIVE_MAP=!1;$jscomp.ASSUME_NO_NATIVE_SET=!1;$jscomp.SIMPLE_FROUND_POLYFILL=!1;
$jscomp.defineProperty=$jscomp.ASSUME_ES5||"function"==typeof Object.defineProperties?Object.defineProperty:function(a,c,b){a!=Array.prototype&&a!=Object.prototype&&(a[c]=b.value)};$jscomp.getGlobal=function(a){return"undefined"!=typeof window&&window===a?a:"undefined"!=typeof global&&null!=global?global:a};$jscomp.global=$jscomp.getGlobal(this);
$jscomp.polyfill=function(a,c,b,d){if(c){b=$jscomp.global;a=a.split(".");for(d=0;d<a.length-1;d++){var e=a[d];e in b||(b[e]={});b=b[e]}a=a[a.length-1];d=b[a];c=c(d);c!=d&&null!=c&&$jscomp.defineProperty(b,a,{configurable:!0,writable:!0,value:c})}};$jscomp.polyfill("Array.prototype.find",function(a){return a?a:function(a,b){return $jscomp.findInternal(this,a,b).v}},"es6","es3");
I do not have such a code in my script: Where does it come from ?
how can I produce the same output as the online version ?

Answer 1

To get the compiler command line work as the web service, I just added an option :
--language_out=ECMASCRIPT_2015

Answer 2

This is likely a discrepancy between the settings on the web service and the ones you're using locally.
Have a look at a Closure Compiler: Flags and Options to see what settings you might prefer.
If you'd share your source, it'd be possible to try and help you narrow down the options.
As for the extra code, I believe it is at least partially a polyfill for Array.prototype.find (aka [].find), which I assume is in your code?
If so, that's Closure injecting code to improve your cross browser compatibility.