如何在AngularJS中保存对象的JSON索引位置，而不是对象本身？

Question

Here is my JSON:

$scope.myjson = [
                   {id: "1", name: "a"},
                   {id: "2", name: "b"},
                   {id: "3", name: "c", children: [{id: "4", name: "d"}]}
               ];

I want to save in javascript the position of object X, for example the position of first object is $scope.myjson[0] , but I don't want to save the object itself, I just want the position. On the same way I want to save $scope.myjson[2].children[0] .

I must save it a string? How than I use it to get that object in O(1)?

Answer 1

Why do you want to save the position of the object and not simply the object itself?

If you're looking to cache objects based on an id lookup something like this would work (completely untested):

var find = (function() {
    var cache = {}, fn; 

    return fn = function(/*array*/ arr, id) {
       if(cache[id]) return cache[id];
       for(var i=0; i < arr.length; i++) {
          if(arr[i].id === id) 
             return (cache[id] = arr[i]);
          if(arr[i].children && val = fn(arr[i].children, id)) 
             return (cache[id] = val);
       }

       return null;
    }
})();

This way subsequent calls to find would return the cached object. Depending on the size of the array and the frequency of lookups, you could also just iterate over it once and create a hash of id => object.