Add new keys and values in a array

Question

I have an array which has multiple keys name and different keys for abteilung:

{abteilung: "Research & Development", name: "Susanne Gast"}, {abteilung: "HR", name: "John Doe"}, {abteilung: "HR", name: "Joe Doe"}...

Now I want to add a key target with a unique id for every name. And I also want to add a key source with an id for every key+value abteilung. There are duplicates for abteilung.

I'm able to add the key+value target. But how can I add the key+value for abteilung

let linksArray = links;
let u = 0, let a = 0, ln = linksArray.length; 
for (u;u<ln;u++){ 
 linksArray[u].target = u+1;
}

Thank your for your hints

• T.J. Crowder: What you have is just an array of objects, no JSON in sight. JSON is a textual notation for data exchange. (More here.) If you're dealing with JavaScript source code, and not dealing with a string, you're not dealing with JSON. (If what you have in your first code block were JSON, it would be invalid JSON, as property names must be in double quotes in JSON.)
• T.J. Crowder: "I'm able to add the key+value target. But how can I add the key+value for abteilung" I don't understand. There already is a property called abteilung. You don't need to add it, it's already there.
• Pointy: It's not clear what you want the "source" value to be.
• mm1975: ok sorry, I need an unique id (key: target) for every name in the array. And i also need a key called source, which should have a unique id. Not in the same range of the target ids because I need the target, source-keys for drawing lines in a graph

Answer 1

For assigning the source, you could first build a Map that has a key for every unique abteilung. The Map values can then become the sequential number. Finally perform a look-up in that Map for each object and assign the retrieved number to the source property:

const links = [{abteilung: "Research & Development", name: "Susanne Gast"}, {abteilung: "HR", name: "John Doe"}, {abteilung: "HR", name: "Joe Doe"}];
const map = new Map(links.map(o => [o.abteilung, 0]));
Array.from(map.keys(), (abteilung, i) => map.set(abteilung, i+1));
links.forEach(o => o.source = map.get(o.abteilung));
console.log(links);

I did not include the assignment to target, as you had that working fine already.

If it is not necessary that the numbering is a sequence without gapes, but gaps are allowed, then you can also assign the sequence number during the Map construction:

var links = [{abteilung: "Research & Development", name: "Susanne Gast"}, {abteilung: "HR", name: "John Doe"}, {abteilung: "HR", name: "Joe Doe"}];
let i = 0;
const map = new Map(links.map(o => [o.abteilung, i++]));
links.forEach(o => o.source = map.get(o.abteilung));
console.log(links);