在JSON中查找一组对象

Question

[
{"id":1,"id_parent":7,"name":"sub category of cat 7-1"}, 
{"id":2,"id_parent":7,"name":"sub category of cat 7-2"},
{"id":3,"id_parent":8,"name":"sub category of cat 8-1"},
{"id":4,"id_parent":8,"name":"sub category of cat 8-2"}
]

I want to find a group of objects in a bigger group. For example, just get objects that have id_parent=7. Now I use a for loop to do that, but I wonder there is any alternative solution to do that. Thank you

Answer 1

If your browser has Array.filter , you could do this:

var children_of_7 = data.filter(function(item) {
    return item.id_parent === 7;
});

If your browser doesn't have it natively, you could shim it .

Answer 2

If you have a browser that provides ECMAScript 5th Edition implementation, than you indeed can do:

var filteredResults = data.filter(function(item) {
  return item.id_parent === 7;
});

otherwise your good ole loop is the solution:

var filteredResults = [];
for (var i = 0, l = data.length; i < l; i++) {
  if (data[i].id_parent === 7) {
    filteredResults.push(data[i]);
  }
}

Keep in mind, however, that, at least AFAIK, filter has performance penalty.

I've mustered up some quick test for reference - can be seen here .

and the difference is substantial.

Answer 3

No, there isn't. All you can do is loop through your JSON.

Answer 4

underscore.js offers some interesting search capabilities:

http://documentcloud.github.com/underscore/