CODEWITHSUNDEEP
javascript
EI-01
EI-01

Reputation: 1095

How to combine filter and reduce on arrays in javascript

I have 2 arrays

var a = [{id: 1, name:"SFO"}, {id:2, name:"ATL"}];

var b = [{number: 1, sourceId:1, destinationId:2}, {number:2, sourceId:2, destinationId:1}];

I want to return an array in this form:

[{source: {name: "SFO"}, destination: {name: "ATL"}}, {source: {name:"ATL"}, destination: {name: "SFO"}}]

How can i use filter and reduce to produce this result above

Upvotes: 1

Views: 699

Answers (2)

CroMagnon
CroMagnon

Reputation: 1208

The code which gets expected array:

var a = [{id: 1, name:"SFO"}, {id:2, name:"ATL"}];
var b = [{number: 1, sourceId:1, destinationId:2}, {number:2, sourceId:2,  destinationId:1}];

var arr = [];
for(var i=0; i<b.length; i++){
    arr.push({
        source: {name: findName(b[i].sourceId, a) },
        destination: {name: findName(b[i].destinationId, a) }
    });
}

function findName(nr, a){
    for(var i=0; i<a.length; i++){
        if(nr==a[i].id){
            return a[i].name;
        }
    }
}

//[{source: {name: "SFO"}, destination: {name: "ATL"}}, {source: {name:"ATL"}, destination: {name: "SFO"}}]
console.log(arr);

Getting expected array using map and filter:

var a = [{id: 1, name:"SFO"}, {id:2, name:"ATL"}];
var b = [{number: 1, sourceId:1, destinationId:2}, {number:2, sourceId:2, destinationId:1}];

var arr = b.map(function(obj){
    return {
        source: { name: a.filter(function(obj2){ if(obj2.id==obj.sourceId) return obj2.name; })[0].name },
        destination: { name: a.filter(function(obj2){ if(obj2.id==obj.destinationId) return obj2.name; })[0].name }
    };
});

//[{source: {name: "SFO"}, destination: {name: "ATL"}}, {source: {name:"ATL"}, destination: {name: "SFO"}}]
console.log(arr);

Upvotes: 1

Nenad Vracar
Nenad Vracar

Reputation: 122027

If you have to do this you can use map() and find() but this is very inefficient and you should change your data structure.

var a = [{id: 1, name:"SFO"}, {id:2, name:"ATL"}];
var b = [{number: 1, sourceId:1, destinationId:2}, {number:2, sourceId:2, destinationId:1}];


var result = a.map(function(e) {
  var o = {}
  o.source = {
    name: e.name
  }
  var destB = b.find(function(f) {
    return e.id == f.sourceId
  })
  if (destB) {
    destB = destB.destinationId
    var destName = a.find(function(x) {
      return x.id == destB
    })
    if (destName) {
      destName = destName.name;
      o.destination = {
        name: destName
      }
    }
  }
  return o
})

console.log(result)

Upvotes: 0

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