foreach array to create new array with nested array

Question

I have array in javascript

Now I have to groupby this array on field entityName and appointmentName to make output like this

• Vassilis Barzokas: And what have you tried already?

Answer 1

You could use the smart Array#forEach with an object for referencing the group.

var companyArr = [{ entityName: "ABC Company, LLC", appointmentName: "ABCware", eventName: "Annual Report", dueDate: "2017-03-01" }, { entityName: "ABC Company, LLC", appointmentName: "ABCware", eventName: "Business Licence Renewal", dueDate: "2017-06-01" }, { entityName: "XYZ Companies, LLC", appointmentName: "XYZWare", eventName: "Annual Report - II", dueDate: "2016-06-27" }],
 newCompanyArr = [];
companyArr.forEach(function (a) {
 var key = a.entityName + '|' + a.appointmentName;
 if (!this[key]) {
 this[key] = { entityName: a.entityName, appointmentName: a.appointmentName, eventArray: [] };
 newCompanyArr.push(this[key]);
 }
 this[key].eventArray.push({ eventName: a.eventName, dueDate: a.dueDate });
}, Object.create(null));
console.log(newCompanyArr);

Answer 2

Made a fiddle for this:

JavaScript

var companyArr = [{
 entityName : "ABC Company, LLC",
 appointmentName : "ABCware",
 eventName: " Annual Report",
 dueDate : " 2017年03月01日"
},{
 entityName : "ABC Company, LLC",
 appointmentName : "ABCware",
 eventName: " Business Licence Renewal",
 dueDate : " 2017年06月01日"
},{
 entityName : "XYZ Companies, LLC",
 appointmentName: "XYZWare",
 eventName : " Annual Report - II",
 dueDate : " 2016年06月27日"
}];
var newCompanyArr = [];
var processedCompanies = [];
for(var i = 0; i < companyArr.length; i++) {
 var company = companyArr[i];
 var key = company.entityName + ' - ' + company.appointmentName;
 if(processedCompanies.indexOf(key) === -1) {
 var results = companyArr.filter(function(comp) {
 return comp.entityName === company.entityName && comp.appointmentName === company.appointmentName;
 });
 var newCompany = {
 entityName: company.entityName,
 appointmentName: company.appointmentName,
 eventArray: []
 }
 for(var y = 0; y < results.length; y++) {
 var res = results[y];
 newCompany.eventArray.push({
 eventName: res.eventName,
 dueDate: res.dueDate
 })
 }
 newCompanyArr.push(newCompany);
 processedCompanies.push(key);
 }
}
console.log(JSON.stringify(newCompanyArr, null, 2));

forEach does not work on all browsers (IE < 9).

Answer 3

Here is a working plnkr

Commented Code

var companyArr = [{
 entityName : "ABC Company, LLC",
 appointmentName : "ABCware",
 eventName: " Annual Report",
 dueDate : " 2017年03月01日"
},{
 entityName : "ABC Company, LLC",
 appointmentName : "ABCware",
 eventName: " Business Licence Renewal",
 dueDate : " 2017年06月01日"
},{
 entityName : "XYZ Companies, LLC",
 appointmentName: "XYZWare",
 eventName : " Annual Report - II",
 dueDate : " 2016年06月27日"
}];
// so we need to group by a particular key, so create the dictionary
var groupByDict = {};
for (var i = 0; i < companyArr.length; i++) {
 var event = companyArr[i];
 // here is the composite key we're going to group by
 var key = event.entityName + " " + event.appointmentName;
 // we need to get the pre-existing group if there is one
 var grouping = groupByDict[key];
 // we use the || to say if there isn't a value, prepopulate it with one
 grouping = grouping || {
 entityName: event.entityName,
 appointmentName: event.appointmentName,
 eventArray: []
 };
 // then we need to push the event details into the event array for this grouping
 grouping.eventArray.push({
 eventName: event.eventName,
 dueDate: event.dueDate
 });
 // then put the grouping back into the group by dictionary
 groupByDict[key] = grouping;
}
// finally you wanted them as an array of groupings
var groupsAsArray = [];
// so here we just iterate through all of the keys in the dictionary
for (var key in groupByDict) {
 if (!groupByDict.hasOwnProperty(key)) continue;
 // if it is a key we care about then push them into the array
 groupsAsArray.push(groupByDict[key]);
}
console.log(groupsAsArray);

• Callum Linington: I still don't understand why there is a downvote on a correct answer that supports ECMA 3 and above. Which is clearly demonstrating the logic behind grouping...