In Typescript 2 how can I take single property from array of objects and assign to new array?

Question

I have this "model" in TypeScript 2:

export class MyModel {
   myProperty1: string;
   myProperty2: string;
   ...
}

I also have this class:

// Leaving out the imports
@Component
...
export class MyClass {
   private myArray: Array<MyModel>;

   ngOnInit() {
      this.myArray = ...// calls a service which returns a populated array of MyModel objects;
   }

   ngAfterViewInit() {
      var newArray: Array<string> = this.myArray ??? // take only myProperty1 from myArray objects and assign to newArray
   }
}

How can I take only the myProperty1 in myArray and assign to my new string array?

So if myArray contains two elements of type MyModel:

[{"one", "apple"}, {"two", "oranges"}]

Then newArray should end up containing these two elements of type string:

["one", "two"]

Suren Srapyan · Accepted Answer · 2017-02-15 16:46:57Z

8

Use map() function.In this case it gets each item in your array, an returns an array of properties, which you select. In my case an array of prop1 .

const arrays = [{prop1: "one", prop2: "apple"}, { prop1: "two", prop2: "oranges"}];

const newArr = arrays.map(item => item.prop1);
console.log(newArr);

edited Feb 15, 2017 at 16:46

answered Feb 15, 2017 at 14:35

Suren Srapyan

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1 Comment

Ruan Mendes Over a year ago

"returns an array of properties, which you select" is not very accurate, it doesn't return an array of properties, it returns an array where each item has been mapped into any value you desire by returning it from the callback function.

Ruan Mendes · Accepted Answer · 2017-02-15 15:38:51Z

7

Use Array.map, it creates a new array by processing each element.

this.myArray.map(o => o.myProperty1)

edited Feb 15, 2017 at 15:38

answered Feb 15, 2017 at 14:33

Ruan Mendes

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