如何将两个集合变成一个

Question

This is as much a basic data structure question as it is a specific implementation question.

I have two collections:

['One', 'Two', 'Three']
[{'Name': 'Two', 'Time': '12:00'}, {'Name': 'Four', 'Time': '14:30'}]

What I want is to merge them into a third collection:

[
    {'Name': 'One', 'HasTime': false, 'Valid': true },
    {'Name': 'Two', 'HasTime': true, 'Valid': true, 'Time': '12:00' },
    {'Name': 'Three', 'HasTime': false, 'Valid': true },
    {'Name': 'Four', 'HasTime': true, 'Valid': false, 'Time': '14:30' },
]

I can do this like in this pseudo-code:

// Pseudo-Code, hence no isOwnProperty and other checks
var r = [];
for(v in one) {
  var obj = { Name: v, Valid: true, HasTime: false };
  for(t in two) {
    if(t.Name === v) {
        obj.HasTime = true;
        obj.Time = t.Time;
        break;
    }
  }
  r.push(obj);
}

for(t in two) {
    var valid = false;
    for(x in r) {
        if(x.Name === t.Name) {
           valid = true;
           break;
        }
    }
    if(!valid) {
      var obj = new { Name: t.name, Valid: false, HasTime: true, Time: t.Time };
      r.push(obj);
    }
}
return obj;

This seems inefficient and I wonder if Angular even already has such a function - my problem is that I don't know what this technique is called. I guess there is a term in Set theory or functional programming, as this is essentially a Union followed by a transform, but the basic term for this in functional programming eludes me - is there a name for this?

Answer 1

You could call that a map-reduce if you want, as you basically need first to transform both arrays to a unified structure ( Map ), and then merge them together ( Reduce ).

However there is nothing magic in it, especially since your structure is totally custom, so you cannot avoid your aglorithm.

You don't really need map-reducing since you only have two arrays, but to give you an idea it would look like this:

var result = [one, two].map(function(arr) {
  // transform arr into {Name, Valid, HasTime} items
}).reduce(function(arr1, arr2) {
  // merge arr1 and arr2
});