将全局变量绑定但不将“ this”绑定到回调函数

Question

Here is an example. I know it doesn't work because bind() just bind the arguments of a function.

global_var = 2
var foo = function(){
  console.log(global_var)
}
var bar = foo.bind(null,/* global_var =*/ 3)
setTimeout(bar)

In my case, foo is from a library so it cannot be modified (not understand why it use global scope), that's why I cannot bind a scope "this" to the function.

bar is going to be a callback, and I want to make sure that it can output '3' every time.

Answer 1

You can always extend your global function. Check the below code snippet.

Hope this helps you!

 var global = 2; //your global library variable var foo = function() { console.log('inside foo library'); }; //make the global function extended foo = (function(oldFn) { function newFoo() { oldFn(); console.log('inside extended function') return 3; } return newFoo; })(foo); //callback variable var bar = foo; console.log(bar());