It is said that forEach() method is used to loop over any array like object .But here
Array.prototype.forEach.call({1:"a",2:"b"},function(eleVal,ele){alert(eleVal+":"+ele)})
The above code dont work ,why??
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3 Answers
Because {1: "a", 2: "b"} is not an array, it's an object. Array.forEach requires that its target has a length property, which this object does not.
Try with an array such as ["a", "b"] and it will work, or alternatively with the array look-alike
{0: "a", 1: "b", length: 2}
4 Comments
Maizere Pathak.Nepal
but it is array like object
Evan Trimboli
It's more akin to a hash. It's not an array.
Jon
@Maizere: The ECMAScript specification details exactly how
.forEach should work. Note that it requires the object to have a length property.Jon
Since there is more than one person downvoting this answer, something must be wrong with it. Can we have some feedback please?
Add a .length property to the object and it'll work.
Please note that you'll index will start at 0, so the first element will be undefined.
[].slice.call({1: 'a', 2: 'b', length: 3})
[undefined × 1, "a", "b"]
Comments
Another way to do it. I prefer this one since it doesn't modify the original object.
var obj = {1:"a", 2:"b"};
for(var i in obj) { if(obj.hasOwnProperty(i)) console.log(i + ':' + obj[i]); }
3 Comments
Xotic750
You can improve your answer by saying why you have demonstrated this form of looping, when the OP has specified the
forEach method. And consider filtering using hasOwnProperty within your loop. Your side effects will be different from the original.
Cesar Castro
@Maizere you said that your code didn't work, I only showed other way to solve the problem. Many people ask why their code doesn't work, when they only don't know a better way to do it. I had the best of intentions.
Maizere Pathak.Nepal
@Seza edit ur question so that i can upvote it ,thank u for ur exercise