gistfile1.js

var val1, val2, val3, str, obj;

str = "info.first_name";

obj = {
  info: {
    first_name: "Bob"
  }
};

val1 = eval("(obj."+str+")");

val2 = (new Function('obj', 'return obj.' + str + ';'))(obj)

for(i = 0, val3 = obj; val3 != undefined && i < str.split(".").length; val3 = val3[str.split(".")[i]], i++);

console.log(val1); // Bob
console.log(val2); // Bob
console.log(val3); // Bob


fetchInObj = function (obj, str) {
  var val, arr;
  arr = str.split(".");
  for(i = 0, val = obj; val != undefined && i < arr.length; val = val[arr[i]], i++);
  return val;
};