javascript - Why does browserify load every module before calling require? -

i have code this:

index.js

var x, = 1;  if (a)    x = require("./a"); else    x = require("./b");  module.exports = x(); 

a.js

console.log("a loaded"); module.exports = function (){     console.log("a running") }; 

b.js

console.log("b loaded"); module.exports = function (){     console.log("b running") }; 

by node got

a loaded running 

but karma+browserify got

a loaded b loaded running 

in console.

is there way prevent b loading browserify?

please, correct me if i'm wrong, way browserify works takes every js file may need, , create single js everything, may used in browser; since can't determine of sources need use @ compile time, need load everything.

maybe try using alternate script loader, requirejs, example.