Javascript, jquery - Call array position by using a variable name

Question

I have 2 arrays:

var array1 = [50,60];
var array2 = [120,180];

I am passing a value to a variable like this:

var curId = $(this).attr('id');

I want to set the content of #result to a computation like this:

$(#result).text(number * curId[0]);

Number is a variable predefined by me, and curId[0] shoul actually translate to array1[0] or array2[0], depending on the css class.

Can anyone tell me the right syntax for this? I'm pretty noob at js. Thanks.

Answer 1

You can use a variable to hold the array that you want to use:

var myArray;

if (something)
    myArray = array1;
else
    myArray = array2;

$('#result').text(number * myArray[0]);

If you're trying to get the array in a variable from a string containing the name of the variable, you should use an object, like this:

var arrays = {
    array1: [50,60],
    array2: [120,180]
};

var myArray = arrays[curId];

$('#result').text(number * myArray[0]);

Answer 2

So curId will be the string "array1" or "array2"? Then you'd do it like this:

var lookups = {
    array1: [50, 60],
    array2: [120,180]
};

var curId = $(this).attr('id');
$('#result').text(number * lookups[curId[0]]);

What that does is create an object (lookups) to contain this information you're looking up. That object has the properties array1 and array1, which are your arrays. You get the string "array1" or "array2" from the ID of your element into the variable curId, and then you use the fact that Javascript lets you look up properties by their name using [] syntax. All of these are the same:

a = lookups.array1;
// is the same as
a = lookups["array1"];
// is the same as
a = lookups["array" + "1"];
// is the same as
s = "array1";
a = lookups[s];

Technically, if your arrays are declared at global scope, you could do that without using the lookups object, but if you're fairly new to Javascript I won't go into why, and regardless, I'd recommend using one.