如何猴子修补在另一个函数中声明的函数

Question

Say I have the following code:

window.foo = function() {
  bar();
  function bar() {
    console.log('hello');
  }
}
/* insert monkey-patching code here */
foo();

What code can I replace /* insert monkey-patching code here */ with in order to make this eg write goodbye instead of hello on the console?

I have tried the following in order to override bar , but it does not work:

window.foo = function() {
  bar();
  function bar() {
    console.log('hello');
  }
}
window.bar = function() {
  console.log('goodbye');
}
window.foo.bar = function() {
  console.log('goodbye');
}
foo();

Answer 1

You can't.

The function is stored in a local variable inside foo . It isn't accessible from outside that function.

You would need to either:

• Replace the whole of foo
• Refactor foo so bar was declared in a wider scope (and accessible from where you want to change it)