TypeError: Cannot read property '0' of undefined TypeError: Cannot read property '0' of undefined

Ionic Framework ionic-v3
1 
public product: any;

loadProducts(){
  this.myProvider.load()
  .then(data => {
    console.log(data);
    this.product= data;
   });
}

this.eventDate=new Date(this.product[0].start_time); //when ı write this code its givin error like this TypeError: Cannot read property ‘0’ of undefined TypeError: Cannot read property ‘0’ of undefined

so plaese help me how can ı use peroducts something like product[0].

2

When you write something like this.product[0].start_time, you are effectively promising that at the time that gets executed:

  • this.product has to be an array
  • the first element of that array must be an object

That isn’t true, hence you see this runtime error. You can move lots of the problem out of runtime and into build time very easily, and this is why I keep begging people to stop abusing any.

Give product a proper type (and a proper name, because it’s a list of products, not a single product). I always add the following three compiler options to my tsconfig.json to help me here:

"noImplicitAny": true,
"strictNullChecks": true,
"strictPropertyInitialization": true,

Our first pass:

export interface Product { // stuff goes here };
public products: Product[];

Now TypeScript will yell at us (helpfully) that products hasn’t been initialized. I don’t know enough about the context of where you are wanting to write the initializer for eventDate to be able to suggest whether it makes more sense to initialize products to something like [{}] or to put an if guard around the problematic line in order to check if this.product[0] is a valid object, but you need to do one of those two things.

4

ı didnt understand can you make advice another way only ı need reach products index

or ı declared new array like this public items:any=[]; how can ı make push element of “product” to “items” array.