split '{a}{b}{c}'?

I have an object that looks like

var obj = {
   a: {
      a: {
         a: 'value'
      }
   },
   b: {
      a: {
         a: 'value2'
      },
      b: {
         a: 'value3'
      开发者_JAVA百科}
   }
}

I have a function which gets given a mask that looks like {b}{a}{a} what I want to do is get the value at obj.b.a.a how can I do this?

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Slice off the first and last character, split by }{, and then recursively access the object with each element in turn (since foo.bar and foo['bar'] are equivalent).

---

This will work if your mask always has three properties. If not, you can write a function that does something similar:

var mask = "{a}{b}{c}";
var props = mask.replace(/{|}/g, "");

obj[props[0]][props[1]][props[2]];

---

obj.getMask = function(s) {
  var o=this, attrs=s.slice(1,s.length-1).split("\}\{");
  while (attrs.length > 0) {
    o = o[attrs.shift()];
    if (!o) return null;
  }
  return o;
};
obj.getMask("{a}{a}{a}"); // => "value"
obj.getMask("{b}{a}{a}"); // => "value1"
obj.getMask("{x}{y}{z}"); // => null

Of course, you can change the signature to pass in "obj" instead of using this if you don't want to muck up the object itself.

---

You can use reduce rather than use recursion. Here's a one-liner:

function index(obj, indexList) {
    return indexList.reduce(function(obj,x){return obj[x]}, obj);
}

function indexWithMask(mask) {
    return index(obj, mask.slice(1,-1).split('}{'));
}

---

Here is my code without using eval. Its easy to understand too.

function value(obj, props) {
  if (!props) return obj;
  var propsArr = props.split('.');
  var prop = propsArr.splice(0, 1);
  return value(obj[prop], propsArr.join('.'));
}

var obj = { a: { b: '1', c: '2', d:{a:{b:'blah'}}}};

console.log(value(obj, 'a.d.a.b')); //returns blah

If you are still using the mask part, you can modify a bit on the code.

function value(obj, props) {
    if (!props) return obj;
    var propsArr = props.match(/\{[a-zA-Z1-9]+\}/g);
    var prop = propsArr.splice(0, 1);
    return value(obj[prop[0].replace('{', '').replace('}', '')], propsArr.join(''));
}