Passing methods as a argument in JavaScript

Question

I'm writing a function which will allow me to display the values of an array by passing another function as a value.

This code works just fine:

function forEach(array, action) {
  for (var i = 0; i < array.length; i++)
    action(array[i]);
}
forEach(["foo", "bar", "qux"], alert);

But it throws and error if I try to pass a function with a property:

function forEach(array, action) {
  for (var i = 0; i < array.length; i++)
    action(array[i]);
}
forEach(["foo", "bar", "qux"], console.log);

If I do this: action.log(array[i]); it works just fine, but that would only allow me to pass functions with a .log property. Is there any way I can write a function which allows me to pass another function and property as a value?

related: How to access the correct this / context inside a callback? - pass console.log.bind(console) instead. — Bergi
– Bergi, Commented Sep 1, 2014 at 14:47

Richard Foster · Accepted Answer · 2014-09-01 14:44:57Z

3

The problem isn't using a method of an object, it's a console.log specific problem. Bug report here. For console.log specifically, you can bind context to it, for example:

forEach(["foo", "bar", "qux"], console.log.bind(console));

Other methods will work fine, for example:

var x = {
    test: function(str){
        alert(str);
    }
}

forEach(["hello", "world"], x.test);

answered Sep 1, 2014 at 14:44

Richard Foster

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Sami · Accepted Answer · 2014-09-01 14:41:25Z

0

You can use something like

function forEach(array, action) {
for (var i = 0; i < array.length; i++)
  action(array[i]);
}
forEach(["foo", "bar", "qux"], function(x){ return console.log(x) });

answered Sep 1, 2014 at 14:41

Sami

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Ovais · Accepted Answer · 2014-09-01 15:07:32Z

0

In Chrome, it is expected because console.info expects its "this" reference to be console, not window. Otherwise, I found it working in Firefox 32 / IE.

https://code.google.com/p/chromium/issues/detail?id=48662

answered Sep 1, 2014 at 15:07

Ovais

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