Count occurrences of each item in JSON [closed]

Question

I want to return the count of each property. For example, I would like to return how many people are in each group. So for the following JSON, it would return 3 people in Group 1, 3 people in Group 3, 2 people in Group 16, etc.

I'm looking for a Javascript or jQuery solution.

Note: I do not need help parsing the JSON. I only need help in finding the counts of each occurrence.

{
"people":[
    {"id":"0","name":"Mike Johnson","group":1},
    {"id":"1","name":"Bob Smith","group":2},
    {"id":"2","name":"Richard Thomas","group":3},
    {"id":"3","name":"Betty White","group":16},
    {"id":"4","name":"Tim Thompson","group":3},
    {"id":"5","name":"Carl Lewis","group":16},
    {"id":"6","name":"Kathy Towers","group":3},
    {"id":"7","name":"Billy Bob","group":1},
    {"id":"8","name":"Sally Bailey","group":1}
    ]
}

Answer 1

Like some comment said, you have to loop through the "people" array. It's easy to turn this "feature" into a function like I have so you can just specify the group you're searching for, and get back the number of people.

http://jsfiddle.net/UdhRW/

var obj = {
  "people": [
    {"id":"0","name":"Mike Johnson","group":1},
    {"id":"1","name":"Bob Smith","group":2},
    {"id":"2","name":"Richard Thomas","group":3},
    {"id":"3","name":"Betty White","group":16},
    {"id":"4","name":"Tim Thompson","group":3},
    {"id":"5","name":"Carl Lewis","group":16},
    {"id":"6","name":"Kathy Towers","group":3},
    {"id":"7","name":"Billy Bob","group":1},
    {"id":"8","name":"Sally Bailey","group":1}
    ]
};

function getCount(group) {
    var count = 0;
    for (var i = 0; i < obj.people.length; i++) {
        if (obj.people[i].group == group) {
            count++;
        }
    }
    return count;
}

getCount(1);   // should return 3

If obj isn't global, you can pass it to the function and it would be like this:

function getCount(arr, group) {
    var count = 0;
    for (var i = 0; i < arr.length; i++) {
        if (arr[i].group == group) {
            count++;
        }
    }
    return count;
}

getCount(obj.people, 1);   // should return 3

Answer 2

You can extract the groups by using something like this:

> var groups = foo['people'].map(function(value, index) {return value['group']});
[1, 2, 3, 16, 3, 16, 3, 1, 1]

From there, just create an object with these keys:

var group_count = {};

groups.forEach(function(value, index) {
    if (value in group_count) {
        group_count[value] += 1;
    } else {
        group_count[value] = 1;
    }
});

This will give you an object that contains the number of occurrences of each group.

Also, this code won't work IE8 and lower, so you'll have to find a forEach and map polyfill somewhere on the web.