CODEWITHSUNDEEP
javascriptloopsbinding
Marc
Marc

Reputation: 3894

for loop, element binding

i have a question about a foor loop. Why is my output every time "C" ?

function Dummy(){}

Dummy.prototype.a = function(){ console.log("Hello from A"); };
Dummy.prototype.b = function(){ console.log("Hello from B"); };
Dummy.prototype.c = function(){ console.log("Hello from C"); };

function hooks(obj){
	for(method in obj){
    original = obj[method];
  	obj[method] = function(){
    	console.log("Overrid %s", method);
      original();
    };
  }
}

var instance = new Dummy();
hooks(instance);

instance.a();
instance.b();
instance.c();

I would to create an hookable middleware

Upvotes: 0

Views: 106

Answers (2)

Mack Cope
Mack Cope

Reputation: 31

You just need to make sure to declare your variables. "method" and "original" were never declared. See the working example below:

function Dummy(){}

Dummy.prototype.a = function(){ console.log("Hello from A"); };
Dummy.prototype.b = function(){ console.log("Hello from B"); };
Dummy.prototype.c = function(){ console.log("Hello from C"); };

function hooks(obj){
	for(let method in obj){
    let original = obj[method];
  	obj[method] = function(){
    	console.log("Overrid %s", method);
      original();
    };
  }
}

var instance = new Dummy();
hooks(instance);

instance.a();
instance.b();
instance.c();

Upvotes: 1

Kenji Mukai
Kenji Mukai

Reputation: 599

Here is the solution code: The reason of this is that when you assign the function to 'original' variable it will always reference the last assignment because the 'original' variable is declared in global scope.

function Dummy(){}

Dummy.prototype.a = function(){ console.log("Hello from A"); };
Dummy.prototype.b = function(){ console.log("Hello from B"); };
Dummy.prototype.c = function(){ console.log("Hello from C"); };

function hooks(obj){
    for(method in obj){
        (function(original, method) {

            obj[method] = function(){
                console.log("Overrid %s", method);
                original();
            };
        })(obj[method], method)
    }
}

var instance = new Dummy();
hooks(instance);

instance.a();
instance.b();
instance.c();

Upvotes: 1

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