How might I be able to use Array.prototype.forEach on an object?

Question

I'm just trying to make a little framework for learning purposes, and I want to be able to use Array.prototype.forEach on objects, this is what I have right now,

var data = { test: 'test' };

Array.prototype.forEach(data, function(key value) {
    console.log(key);
});

But I get an error, I'm sure you guys can see why, but I can not :) So any help would be great thanks :)

Answer 1

Objects are not arrays, and don't have access to the array prototype. You can just loop over the properties.

for(var key in data){
      console.log(key) //or data[key] if you want the values
   }

with regards to the jQuery comment below, it appears they use loops internally for their "each" function. From the source:

// args is for internal usage only
each: function( obj, callback, args ) {
    var value,
        i = 0,
        length = obj.length,
        isArray = isArraylike( obj );

    if ( args ) {
        if ( isArray ) {
            for ( ; i < length; i++ ) {
                value = callback.apply( obj[ i ], args );

                if ( value === false ) {
                    break;
                }
            }
        } else {
            for ( i in obj ) {
                value = callback.apply( obj[ i ], args );

                if ( value === false ) {
                    break;
                }
            }
        }

    // A special, fast, case for the most common use of each
    } else {
        if ( isArray ) {
            for ( ; i < length; i++ ) {
                value = callback.call( obj[ i ], i, obj[ i ] );

                if ( value === false ) {
                    break;
                }
            }
        } else {
            for ( i in obj ) {
                value = callback.call( obj[ i ], i, obj[ i ] );

                if ( value === false ) {
                    break;
                }
            }
        }
    }

    return obj;
},