my problem is that i have a json-object with and array into here an example.
var object = {
'items':['entry1','entry2']
}
I want to access 'entry2' over a constant string that I receive and shouldn't be changed.
var string = 'items[1]';
The only way I'm solving this problem is over the eval function...
eval('object.'+string);
This returns me entry2.
Is there any other way to achieve this without using eval()?
Like object[string] or object.string
Supposing your string is always the same form, you could extract its parts using a regex :
var m = string.match(/(\w+)\[(\d+)\]/);
var item = object[m[1]][+m[2]];
Explanation :
The regex builds two groups :
(\w+) : a string
\[(\d+)\] : some digits between brackets
and those groups are at index 1 and 2 of the array returned by match.
+something parses the number. It's not strictly needed here as the array accepts a string if it can be converted but I find the code more readable when this conversion is explicited.
On top of dystroy's anwser, you can use this function:
function getValueFromObject(object, key) {
var m = key.match(/(\w+)\[(\d+)\]/);
return object[m[1]][+m[2]];
}
Example:
var object = {
'items':['entry1','entry2']
}
var string = 'items[1]';
var value = getValueFromObject(object, string); //=> "entry2"
First, you can get the array from inside:
var entries = object.items // entries now is ['entry1','entry2']
Then you need to index that to get the second item (in position 1). So you achieve what you want with:
var answer = entries[1] // answer is now 'entry2'
Of course, you can combine this to get both done in one step:
var answer = object.items[1] // answer is now 'entry2'
... I can see this is a contrived example, but please don't call your Objects 'object', or your Strings 'string' :s
try something like this
object.items[1];
string?