How to define Map as argument in angular TypeScript method?

Question

I would need some help, because I am stuck. I have problems defining a simple method in angular4 (TypeScript) that gets an argument of the type Map. All I want is to iterate over the elements in the Map. Nothing special.

When I try to iterate over the Map object map2 I get the following error.

Error: ERROR TypeError: map2.forEach is not a function

doStuff(map2: Map<string, string>):number{
  //I get an ERROR here, because map2 is not recognised as a Map()?
  map2.forEach((value: string, key: string) => {
  console.log(key, value);  
  });

  let map = new Map();
  map.set("A","B");
  map.set("C","d");

  console.log(map.get("A")+" :"+ map.size);
  //THIS WORKS
  map.forEach((value: string, key: string) => {
  console.log(key, value);
   });
    }
});

This is how I call the method from another method

...
//some other method
let map4 = JSON.parse('{ "myString": "string", "myNumber": "4" }');
this.myNumber = this.doStuff(map4);
...

How are you calling the function? What are you passing to it? — Ingo Bürk
– Ingo Bürk, Commented Jun 10, 2018 at 20:29
Your call to JSON.parse returns an anonymous object; it does not return a Map. — cartant
– cartant, Commented Jun 10, 2018 at 21:14

Alberto Trindade Tavares · Accepted Answer · 2018-06-10 21:18:59Z

2

You need to convert a literal object (that is returned by JSON.parse) into a Map to pass it to doStuff. You can use Object.entries (available from ES2017) for that:

let map4 = JSON.parse('{ "myString": "string", "myNumber": "4" }');
this.myNumber = this.doStuff(new Map(Object.entries(map4)));

answered Jun 10, 2018 at 21:18

Alberto Trindade Tavares

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