Is it possible to reference an anonymous array in a for loop?

Question

for (var name in ['dog','cat','cow']) { alert(name); } 

name here returns the index of the array, but I cannot reference it, since it is anonymous.

I know that I can declare it outside the loop, but here I ask if there is a way to refer to a name directly that does not have an index.

Answer 1

If you know that the keys of the array will be integer, then nothing requires using the for..in construct.

 for (var arr = ['dog','cat','cow'], name = 0; name < arr.length; name++ ) { console.log(arr[ name ]); } 

In the above code, a simpler for loop allows you to create a new object and reference the key inside the loop.

Answer 2

... not. At least not, not your own cycle. However, there is ES5 forEach :

 ['dog', 'cat', 'cow'].forEach(function(value, key) { // do stuff }); 

This is practically the same. It supported mostly everywhere , except for the old IE: something like es5-shim , for example, includes ES5 methods even in such old browsers.

Answer 3

You have several options.

If you are using jQuery, you can do this:

 $.each(['dog','cat','cow'], function() { var name = this; alert(this); }); 

If you are not using jQuery, you can create your own function

 function each(array, pFunction) { for(var i = 0; i < array.length; i++) { var element = array[i]; pFunction(element); } } each(['dog','cat','cow'], function(name) { alert(name); }); 

If you don't want to create a function, you can always do something crazy like this: (not recommended)

 for (var name in { 'dog' : '','cat' : null,'cow' : null }) { alert(name); } 

Answer 4

If the array is anonymous, you cannot reference its elements using the for in loop.

Answer 5

No, you cannot do this. It will only show indexes. Also, for looping for an array in JavaScript is bad practice. It will go through the entire array object method.

Answer 6

Massive methods forEach , map , filter , etc. will iterate over the literal indexes of the array:

 ['dog', 'cat', 'cow'].forEach(alert); 

Gasket for older browsers:

 if(![].forEach){ array.prototype.forEach= function(fun, scope){ var T= this, L= T.length, i= 0; if(typeof fun== 'function'){ while(i< L){ if(i in T){ fun.call(scope, T[i], i, T); } ++i; } } return T; } } 

Answer 7

The wrong syntax construct is used for this.

for in intended to enumerate the properties of an object, and not to iterate through arrays. Declare your array outside and use a regular loop.

 var arr = ['dog', 'cat', 'cow']; for(var i = 0; i < arr.length; i++) { // your code }