Using an integer as a key in an associative array in JavaScript

Question

When I create a new JavaScript array, and use an integer as a key, each element of that array up to the integer is created as undefined.

For example:

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Answer 1

As people say, JavaScript will convert a string of number to integer, so it is not possible to use directly on an associative array, but objects will work for you in similar way I think.

You can create your object:

var object = {};

And add the values as array works:

object[1] = value;
object[2] = value;

This will give you:

{
  '1': value,
  '2': value
}

After that you can access it like an array in other languages getting the key:

for(key in object)
{
   value = object[key] ;
}

I have tested and works.

Answer 2

Use an object - with an integer as the key - rather than an array.

Answer 3

Get the value for an associative array property when the property name is an integer:

Starting with an associative array where the property names are integers:

var categories = [
    {"1": "Category 1"},
    {"2": "Category 2"},
    {"3": "Category 3"},
    {"4": "Category 4"}
];

Push items to the array:

categories.push({"2300": "Category 2300"});
categories.push({"2301": "Category 2301"});

Loop through the array and do something with the property value.

for (var i = 0; i < categories.length; i++) {
    for (var categoryid in categories[i]) {
        var category = categories[i][categoryid];
        // Log progress to the console
        console.log(categoryid + ": " + category);
        //  ... do something
    }
}

Console output should look like this:

1: Category 1
2: Category 2
3: Category 3
4: Category 4
2300: Category 2300
2301: Category 2301

As you can see, you can get around the associative array limitation and have a property name be an integer.

NOTE: The associative array in my example is the JSON content you would have if you serialized a Dictionary<string, string>[] object.

Answer 4

You can just use an object:

var test = {}
test[2300] = 'Some string';