Question

I have a string: items[0].name that I want to apply to a JSON object: {"items":[{"name":"test"}]} which is contained in the variable test. I want to apply that string to the object in order to search it (test.items[0].name). I can only think of one way to do this: parse the square brackets and dots using my own function. Is there another way I can do this? Perhaps using eval? (Even though I’d LOVE to avoid that…)

For clarity:
I have a JSON object, what is inside of it is really irrelevant. I need to be able to query the object like so: theobject.items[0], this is normal behaviour of a JSON object obviously. The issue is, that query string (ie. items[0]) is unknown – call it user input if you like – it is literally a string (var thisIsAString = "items[0]"). So, I need a way to append that query string to theobject in order for it to return the value at theobject.items[0]

Answer 1

function locate(obj, path) {

  path = path.split('.');
  var arrayPattern = /(.+)\[(\d+)\]/;
  for (var i = 0; i < path.length; i++) {
    var match = arrayPattern.exec(path[i]);
    if (match) {
      obj = obj[match[1]][parseInt(match[2])];
    } else {
      obj = obj[path[i]];
    }
  }

  return obj;
}

var name = locate(test, 'items[0].name');