Converting javascript string to code without using eval

Question

I'm trying to do the below without using eval() as so many posts say it's slow and evil so you shouldn't use it as there's always alternative ways.

The JS (note i'm using jquery)

$('a').click(function() {

//Assign myVar to the id value of the a tag 
var myVar = $(this).attr('id');


$.getJSON("assets/js/json.js", function(json) {
    alert("json."+myVar+".thumb");
    }); 

});

And i have some basic html, which passing in the value for myVar

<a id="imageID1" href="#">A link 1</a><br />
<a id="imageID2" href="#">A link 2</a>

Basic JSON file

   {
"imageID1" : {
    "thumb" : "assets/images/312px.png",
    "zoomThumb" : "assets/images/gallery/_AR_0063_m_thumb.jpg",
    "large" : "assets/images/gallery/_AR_0063.jpg"
},

 "imageID2" : {
    "thumb" : "another.png",
    "zoomThumb" : "assets/images/gallery/_anotherb.jpg",
    "large" : "assets/images/gallery/another.jpg"
}

  }

So the ID for each link is passed to myVar on click, this is working fine but the alert value isn't correct.

For example if imageID2 is click the alert should actually display "another.png" but instead it's displaying the code i actually want to run, "json.imageID@.thumb".

Now i can change the alert line to

   alert(eval("json."+myVar+".thumb"));

Which does the trick, but as mentioned don't want to use eval due to the know issues.

So any alternative way of doing the above. Thanks in advance for any help or tips.

Ben

possible duplicate of [How to access object using dynamic key?](http://stackoverflow.com/questions/6921803/javascript-how-to-access-json-object-using-dynamic-key) — Felix Kling, Sep 12 '11 at 16:16

score 4 · Accepted Answer · answered Sep 12 '11 at 16:15

4

You're trying to write

alert(json[myVar].thumb);

Indexer notation can be used to retrieve a property by name at runtime.

answered Sep 12 '11 at 16:15

SLaks

868,454
176
1,908
1,964

Nice one thanks Slaks. Was sorting of trying that, but with an additional . alert(json.[myVar].thumb); – Ben Sep 12 '11 at 16:18

score 1 · Answer 2 · answered Sep 12 '11 at 16:18

1

This should work, I believe: alert(json[myVar].thumb);

answered Sep 12 '11 at 16:18

JoshNaro

2,047
2
20
40

Converting javascript string to code without using eval

2 Answers2