Lodash group by multiple properties if property value is true

Question

I have an array of vehicles that need to be grouped by make and model, only if the 'selected' property is true. The resulting object should contain properties for make model and count. Using lodash, how can I organize the vehicle objects into the desired result objects. I'm able to get the vehicle objects grouped by makeCode but I'm not sure how to group by more than one property.

group by make code works

      var vehicles = _.groupBy(response.vehicleTypes, function(item)       {         return item.makeCode; // how to group by model code as well       }); 

initial vehicles

{     id: 1,      selected: true,      makeCode: "Make-A",      modelCode: "Model-a",      trimCode: "trim-a",      yearCode: "2012" }, {     id: 2,      selected: false,      makeCode: "Make-A",      modelCode: "Model-a",      trimCode: "trim-a",      yearCode: "2013" }, {     id: 3,      selected: true,      makeCode: "Make-B",      modelCode: "Model-c",      trimCode: "trim-a",      yearCode: "2014" }, {     id: 25,      selected: true,      makeCode: "Make-C",      modelCode: "Model-b",      trimCode: "trim-b",      yearCode: "2012" }, {     id: 26,      selected: true,      makeCode: "Make-C",      modelCode: "Model-b",      trimCode: "trim-a",      yearCode: "2013" } 

result object

{     Make-A: {         Model-a: {             count: 1         }     } },  {     Make-B: {         Model-c: {             count: 1         }     } }, {     Make-C: {         Model-b: {             count: 2         }     } } 

Answer 1

I am not sure if this will solve Your problem, but in group_by You can add custom logic which allow You to create composite key.

Remember that SEPERATOR value should be defined accordingly to data source You work with, if "--" characters occur in model or type You should not used them as it will not allow You to reverse the process of grouping.

const SEPERATOR = "--"; _.chain(data).filter((item) => item.selected).groupBy((item)=>`${item.model}${SEPERATOR}${item.type}`).value(); 

Answer 2

Since you're already using lodash, you can take advantage of the _.filter function. This will return only the items where selected is true.

var selectedVehicles = _.filter(response.vehicleTypes, 'selected'); 

Now that you have the selectedVehicles array, you can use your original code for grouping by the makeCode.

selectedVehicles = _.groupBy(selectedVehicles, function(item) {   return item.makeCode; }); 

This returns an object, so we will need to iterate through those keys, and perform our second groupBy

_.forEach(selectedVehicles, function(value, key) {   selectedVehicles[key] = _.groupBy(selectedVehicles[key], function(item) {     return item.modelCode;   }); }); 

From this you will have an object of the form. I'll leave it to you to get the count from each array.

{ 'Make-A': { 'Model-a': [ ... ] },   'Make-B': { 'Model-c': [ ... ] },   'Make-C': { 'Model-b': [ ..., ... ] } }