Remove unused javascript code based on coverage report

Question

There is a big javascript library (~ 40 000 lines of code) and an application which uses less than 50% of the library\'s code.

There is a test which uti

Answer 1

Closure Compiler provides some quite advanced unused code clean up features. Some examples:

Removing a dead code block

function hello(name) {
  alert('Hello, ' + name);
}

function hi(name) {
    alert('Hi, ' + name);
}

hello('New user 1');
hello('New user 2');

Compiles to:

alert("Hello, New user 1");
alert("Hello, New user 2");

completely stripping away the hi function and inlining hello. (live demo)

Moving to a more complicated case

As the code gets more complicated, it finds new ways to optimize. For example:

let greeted = 0;

function hello(name) {
  greeted += 1;
  alert('Hello, ' + name);
}

function hi(name) {
  greeted += 1;
  alert('Hi, ' + name);
}

hello('New user ' + greeted);
hello('New user ' + greeted);

Becomes:

var a = 0;
function b() {
  var c = "New user " + a;
  a += 1;
  alert("Hello, " + c);
}
b();
b();

(live demo)

Make sure you turn on the ADVANCED_OPTIMIZATIONS compilation level to enable dead code removal.