Array as class member is undefined in Typescript

Question

I'm trying to add an array as a class member in Typescript. But when I try to access it somewhere I get an error that it is undefined. What am missing here?

.html

<button id="storePersonBtn">

.ts

export class App {

    public myArray: Array<Boolean> = [];

    constructor() {
        console.log(this.myArray) //outputs []
        $('#storePersonBtn').click(this.storePerson);
    }

    private storePerson() {
        console.log(this.myArray) //outputs undefined
    }
}

TPReal · Accepted Answer · 2019-07-25 11:59:35Z

1

The problem is JavaScript's this which is bound at the call site. If you write a.b() then this inside b will be set to a. But if you do this:

const b = a.b;
b();

then this inside b is unset.

What you should do is this:

.click(() => this.storePerson())

This way you call storePerson with the proper this.

answered Jul 25, 2019 at 11:59

TPReal

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