How to update the value of an existing key of a map in Angular 4+

Question

Is there any way to update the value of a created key value pair map in angular 4+.

say i have:

testMap: Map<number, string> = new Map<number, string>();

ngOnInit() {
    this.testMap.set(1, "A");
    this.testMap.set(2, "B");
    this.testMap.set(3, "C");
    this.testMap.set(4, "D");
    this.testMap.set(5, "E");
}

changeValue(id){
    //id is the one of the keys of the map whose value needs to be altered
    //let say (id=3)
    this.testMap.put(id,"ChangedValue"); //PUT is from java
}

Use `set` again. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/set — Frank Modica, Oct 29 '18 at 01:40
To who had MARKED my question DUPLICATE: My question is not to add DYNAMICALLY. My scenario is where ill create key value pair when component load and might have to change the value for particular key when needed later in the process. Hope this helps. — Vithushan, Oct 29 '18 at 03:21

score 11 · Accepted Answer · answered Oct 29 '18 at 01:40

11

You can just you set:

this.testMap.set(id, "ChangedValue")

answered Oct 29 '18 at 01:40

lupus137

383
3
10

1

Thanks. This works. What if the map contains an object as value. Say {id:number, name:string}. Will i be able to change the name only of the object for matched key while having the same id inside the object. Or should i update as whole object – Vithushan Oct 29 '18 at 03:27
3

If you want to update a property of an object in a Map all you need to do is get the object and change the property. `const obj = myMap.get(key); obj.name = "new name";` that's it, the object is by reference so it will automatically be reflected in the entry stored in the Map. – JaredMcAteer May 28 '20 at 19:55
You could also do `const obj = myMap.get(key); myMap.set(key, {...obj, name})` – Scott Wager Dec 26 '20 at 11:57

How to update the value of an existing key of a map in Angular 4+

1 Answers1