下划线将对象转换为数组并按键名排序

Question

I've been using the below code to transform a large list of dates in a array of counts which i can then use in a simple line chart. The issue i'm encountering is with sorting the values by the year and week number. When i have data such as [{201501: 20},{201502: 20},{201451: 20},{201452: 20}] i need to sort the array by the key name into the following format [{201451: 20},{201452: 20},{201501: 20},{201502: 20}] . They i simply discard the key with _.values()

How do i go about ordering the array with underscore, i've tried a few things but i'm pretty lost at this point.

    var graphData = _.chain(thisYearFiltered)
    // map each string like '2014-01-01 00:00:00' using moment.js to the ISO Week. ISO weeks are used because they run Monday to Sunday
    .map(function(date){ 
        return moment(date, "YYYY-MM-DD HH:mm:ss").isoWeekYear() + moment(date, "YYYY-MM-DD HH:mm:ss").isoWeek(); 
    })
    // Manipulate weeks numbers [201423,201423,201423,201423,201424] into a count for each like [{201423:4 },{201424:1}]
    .countBy(function(num) {
        //console.log(num);
        return num;
    })
    // Pull out the values of the objects and discard the week number. [{23:4 },{24:1}] to [4,1]
    .values()
    .value();

I know this is all possible with underscore but i've hit a wall with this one so any suggestions would be welcome.

I've looked into _.sortBy() but that seems to expect a named key to sort on and in my case the keys names are all different. Could i do something similar with the first key?

Answer 1

For objects, sortBy also passes the key to the callback as the second argument and only keeps the value of the object after sorting it, so:

_.chain([201423, 201423, 201423, 201423, 201424]).
   countBy(function(n) { return n; }).
   sortBy(function(v, k) { return k; }).
   value()

gives

[ 4, 1 ]