I am getting an error when using JSON.parse()

```
$jsonStr = JSON.parse(["a:5:{i:0;s:4:"3900";i:1;s:4:"3892";i:2;s:4:"3896";i:3;s:4:"3894";i:4;s:4:"3902";}"])

```

I have used below, but what I need to do is get the content out, loop through it. I need to get 3900, 3892, 3896, 3894, 3902, those are ids, that I need to loop through them and attach to URL, I can attach to URL, I just need to loop through the string and get those ID's out. I don't have to use JSON.parse, I just need to use javascript.

`var jsonStr=$jsonStr;
 var json=JSON.stringify(jsonStr);
 json=JSON.parse(json)`