alternatives to eval() in javascript, nested objects

Question

Eval seems to be generally regarded as a bad idea.

Is there an elegant solution to an eval on nested objects.

So my eval is

eval( "$scope" + lookup_string)

As Javascript opbjects seem to be assoiative arrays, I tried

$scope[lookup_string]

This worked fine until I got to some nested objects.

so if my string contains dots, e.g

lookup_string = "object1.object2.object3"

This works as an eval. But not as an associative_array lookup, as it is treating the string as one, not as three nested lookups.

Now I know I can split the string, and lookup each part, but this seems a fair bit work (compared to eval-ing the string).

Are there any other clean / elegant alternatives to this?

possible duplicate of [Convert Javascript string in dot notation into an object reference](http://stackoverflow.com/questions/6393943/convert-javascript-string-in-dot-notation-into-an-object-reference) — Quentin, Sep 02 '13 at 11:14
Ok, different question, but same answer at the end of the day. Though if there are other alternatives, I would like to see them. — wobbily_col, Sep 02 '13 at 11:25

arb · Answer 1 · 2013-09-02T17:58:40.530

Simple while loop is usually enough for this problem.

function nameSpace(obj, path) {
  var property, 
      path = path.split('.');
  while (property = path.shift()) {
    if (typeof obj[property] === 'undefined')
      return undefined;
    obj = obj[property]
  }
  return obj
}

UPDATE

Well if you just want to use vanilla AND you are certain that the environment you are developing in supports ECMA-5, you can do something like this

function namespace(object, path) {
   var result = path.split('.').reduce(function (value, index) {
        return value[index]
    }, object)
   return result;
}
console.log(namespace(obj, 'a.b.value'))

You could also use a library like lodash to add reduce if it's not natively implemented.

That's ten lines compared to one eval line. Having looked up the reasons for eval being bad (security, debugging, speed), as this is an internal app, I don't see using eval being such a problem, if this is the alternative. — wobbily_col, Sep 02 '13 at 12:46

Marco Plaza · Answer 2 · 2020-06-16T23:03:38.913

This one works with array items:

var oTest = {
    "mypc": {
        "cpu": {
            "cores": 1,
                "manufacturer": "",
                "model": "",
                "speed": 0
        },
            "group": "",
            "hdds": [{
            "capacitygb": 0,
                "driveletter": "c",
                "hddid": "a18822e92ff6e14cbc905bf4df13f8d3",
                "manufacturer": "",
                "port": 0,
                "type": ""
        }]
    }
};


var getProperty = function (obj, path) {
    return path.split(/(\[|\]|\.)/).reduce(function (x, y) {
        return ('[].'.indexOf(y) > -1) ? x : (x === Object(x) && y in x) ? x[y] : undefined;
    }, obj)
}

console.log(oTest.mypc.hdds[0].hddid)
console.log( 'ok: '+ getProperty(oTest, 'mypc.hdds[0].hddid')) 
console.log( 'undefined path: '+ getProperty(oTest, 'mypc.hdds[10].hddid'))

alternatives to eval() in javascript, nested objects

2 Answers2