如果使用&&将语句声明为“后卫”，则闭包编译器不会将其弄平

Question

I don't understand why CC didn't codegolf this further. I frequently write with "guard" statements like var x = obj.fun && obj.fun(); for example. But CC doesn't reduce an if into a "guard".

Are the compiled js and expected js actually different?

Uncompiled source:

window.test = function () {
  var ret = false;
  if (Math.random) {
    ret = Math.random() < 0.5;
  }
  return ret;
}

Command

npx google-closure-compiler \
--compilation_level ADVANCED \
--js test.js \
--js_output_file out.js

Compiled output (prettified):

window.test = function() {
  var a = !1;
  Math.random && (a = 0.5 > Math.random());
  return a;
};

Expected output ("What I would have done"):

window.test = function () {
  return Math.random && 0.5 > Math.random();
}

Answer 1

This code returns undefined if the Math.random function does not exists:

return Math.random && 0.5 > Math.random();

I think that there may be a difference between returning false and returning undefined .