如何使用文本输入中的字符串变量来引用同名的数组

Question

I have a number of arrays in a javascript file The array that I want to use in my calculations is:

 var planets_num = []

If I want to use a certain array, I simply use:

  arraytouse = planets_num

What I want to do is use an input:

 <input type="text" id="mynewtext" value="Enter array name to use">

and then a function to get the value of "mynewtext":

 function getnewform1 () {
 newtext=document.getElementById('mynewtext').value
 . . .
 }

let's say that the var newtext = "abc" I then want:

 abc = planets_num

ie the values from the array abc to be placed in the planets_num array

Hope this makes sense

TIA

Answer 1

If planets_num is in global scope, you can also refer to it like this:

arraytouse = window['planets_num'];

Variables on objects are also indexable values on that object by the same name. For global scope variables, they're on the window object.

So you could do something like this:

arraytouse = window[document.getElementById('mynewtext').value];

If the arrays aren't in global scope then you can organize them as properties on some object and reference that object in the same way:

arraytouse = objectOfArrays[document.getElementById('mynewtext').value];

Answer 2

@David answer is cleaner is more efficient, but here is an alternative with an eval :

var my_array = [];

$("button")[0].onclick = function()
{
    var input_text = $("input")[0].value;
    var array_input = eval(input_text);
}

The fiddle is here:

http://jsfiddle.net/W3NW9/3/

Answer 3

Rather than creating global variables, you should consider using an object and properties:

var data = {
  planets_num: [],
  another_arr:[]
}

Now you can do:

var arraytouse = data[document.getElementById('mynewtext').value];

but of course you should be writing robust code like:

var input = document.getElementById('mynewtext');

// Make sure an element was found before trying to access its value
var arraytouse = input && data[input.value];

// Make sure the value resolved to something truthy before
// trying to use it
if (arraytouse) {
  ...
}