Javascript - array of custom object initialization

Question

How can I initialize an array of custom objects in javascript to prevent the error "Cannot read property 'length' of undefined"?

component

export class MyClass implements OnInit {

  myArray: MyObject[];

}

view

<div *ngIf="myArray.length > 1">Size is greater than 1</div>

The code above rightly gives the mentioned error. What is the right way to initialize the array? Thanks.

Suren Srapyan · Accepted Answer · 2017-10-17 10:42:24Z

2

You have given only the type of your field. You also need to initialize it to refer to something

export class MyClass implements OnInit {

  myArray: MyObject[] = [];

}

Also you have different name in the template, I think it is only typo

<div *ngIf="myArray.length > 1">Size is greater than 1</div>

edited Oct 17, 2017 at 10:42

answered Oct 17, 2017 at 10:41

Suren Srapyan

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5 Comments

Suren Srapyan Over a year ago

@ÁlvaroTouzón Why?

Álvaro Touzón Over a year ago

you have no elements, and he need 1?

Suren Srapyan Over a year ago

Why do you think that he need 1? I don't think he put the full template to work with this. It is only a part of his template. There may be another logic also to push into this items. So actually we can't say what he want to do with that template

Suren Srapyan Over a year ago

@ÁlvaroTouzón Thanks

esseara Over a year ago

SurenSrapyan yes, it was a typo. Your answer is correct, thanks. Álvaro Touzón the array is filled dynamically later in the code, that's why I need to check the size. Thanks to you too.

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