I used to work on this. Happy to answer questions. Here is a good article about Closure Compiler optimizations which J2CL uses as its optimizing compiler: http

I used to work on this. Happy to answer questions. Here is a good article about Closure Compiler optimizations which J2CL uses as its optimizing compiler: https://medium.com/@thomasdeegan/10-optimizations-closure-compiler-can-do-and-uglify-friends-cant-6dca4232299f https://medium.com/@thomasdeegan/10-optimizations-closure-co... This website has Closure Compiler compiled by J2CL running in the browser itself! https://closure-compiler-debugger.appspot.com/j2cl_debugger.html#input0%3Dclass%2520A%2520%257B%250A%2520%2520method%28%29%2520%257B%250A%2520%2520%2520%2520console.log%28%2522A%2522%29%253B%250A%2520%2520%257D%250A%257D%250A%250Aclass%2520B%2520%257B%250A%2520%2520method%28%29%2520%257B%250A%2520%2520%2520%2520console.log%28%2522B%2522%29%253B%250A%2520%2520%257D%250A%257D%250A%250A%252F**%2520%2540return%2520%257BA%257D%2520*%252F%250Afunction%2520getA%28%29%2520%257B%250A%2520%2520return%2520new%2520A%28%29%253B%250A%257D%250A%250Alet%2520a%2520%253D%2520getA%28%29%253B%250Alet%2520b%2520%253D%2520new%2520B%28%29%253B%250A%250A%252F%252F%2520Statically%2520infer%2520A%2523method%2520or%2520B%2523method%2520in%2520a%2520dynamic%2520language%250Aa.method%28%29%253B%250Ab.method%28%29%253B%26conformanceConfig%26externs%3Dvar%2520console%2520%253D%2520%257B%257D%253B%250A%252F**%2520%2540param%2520%257Bstring%257D%2520s*%252F%250Aconsole.log%2520%253D%2520function%28s%29%2520%257B%257D%253B%26refasterjs-template%26TRANSPILE%3Dtrue%26CHECK_SYMBOLS%3Dtrue%26CHECK_TYPES%3Dtrue%26COMPUTE_FUNCTION_SIDE_EFFECTS%3Dtrue%26FOLD_CONSTANTS%3Dtrue%26DEAD_ASSIGNMENT_ELIMINATION%3Dtrue%26INLINE_CONSTANTS%3Dtrue%26INLINE_FUNCTIONS%3Dtrue%26COALESCE_VARIABLE_NAMES%3Dtrue%26INLINE_VARIABLES%3Dtrue%26FLOW_SENSITIVE_INLINE_VARIABLES%3Dtrue%26SMART_NAME_REMOVAL%3Dtrue%26REMOVE_DEAD_CODE%3Dtrue%26REMOVE_UNUSED_PROTOTYPE_PROPERTIES%3Dtrue%26REMOVE_UNUSED_CLASS_PROPERTIES%3Dtrue%26REMOVE_UNUSED_VARIABLES%3Dtrue%26COLLAPSE_VARIABLE_DECLARATIONS%3Dtrue%26COLLAPSE_ANONYMOUS_FUNCTIONS%3Dtrue%26CONVERT_TO_DOTTED_PROPERTIES%3Dtrue%26LABEL_RENAMING%3Dtrue%26COLLAPSE_PROPERTIES%3Dtrue%26DEVIRTUALIZE_PROTOTYPE_METHODS%3Dtrue%26DISAMBIGUATE_PROPERTIES%3Dtrue%26AMBIGUATE_PROPERTIES%3Dtrue%26VARIABLE_RENAMING%3Dtrue%26PROPERTY_RENAMING%3Dtrue%26OPTIMIZE_CALLS%3Dtrue%26OPTIMIZE_PARAMETERS%3Dtrue%26OPTIMIZE_RETURNS%3Dtrue%26CLOSURE_PASS%3Dtrue%26CROSS_MODULE_CODE_MOTION%3Dtrue%26CROSS_MODULE_METHOD_MOTION%3Dtrue%26includeDefaultExterns%3Dtrue https://closure-compiler-debugger.appspot.com/j2cl_debugger....