Can't return a property of object from a JavaScript function

Question

I have a JavaScript function:

function test(arr, index) {
    for (var i = 0; i < arr.length; i++) {
        console.log(arr[i].index);
    }
}

I call the function like this:

test(myArr, 'name')

But it returns undefined. When I use function directly, like this, it works:

for (var i = 0; i < myArr.length; i++) {
    console.log(myArr[i].name);
}

This is my array:

var myArr = [{name: "hamed"}, {name: "hamed1"}]

I don't think I should use single quotes when I call a function but without quotes it does not work either.

When you are doing arr[i].index, you are actually looking for property named index at ith index. — Aniket Sinha
– Aniket Sinha, Commented Jan 8, 2016 at 22:32

tcigrand · Accepted Answer · 2016-01-08 22:13:17Z

9

When you want to access the property by a variable, use bracket notation. This will evaluate the variable and then find that in the object.

function test(arr, index) {
    for (var i = 0; i < arr.length; i++) {
        console.log(arr[i][index]);
    }
}

answered Jan 8, 2016 at 22:13

tcigrand

2,3872 gold badges16 silver badges26 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1