CODEWITHSUNDEEP
javascripttypescriptknockout.jsknockout-2.0knockout-3.0
Anany Shah
Anany Shah

Reputation: 27

What is difference between KnockoutObservable<string[]> and KnockoutObservable<string>[]

What is difference between KnockoutObservable<string[]> and KnockoutObservable<string>[] When to use either of them?

Upvotes: 0

Views: 949

Answers (2)

Ryan Leach
Ryan Leach

Reputation: 4470

If you want an Observable Array, you should be using https://knockoutjs.com/documentation/observableArrays.html

Unless the typescript facade is doing something unexpected (I'm unfamiliar with it), chances are both an array of Knockout Observables, or a Knockout Observable of type array are going to be incorrect.

But to answer your question, they are going to have very different performance overheads, and different uses.

A plain KnockoutObservable of type array, is only going to update when the entire array is replaced. you will not receive notifications when the array is mutated, I can't think of any reason off the top of my head for using it, except for maybe some really data heavy operations, where you are receiving a stream of array information.

However, an array of KnockOut Observables, will give a really heavy performance overhead.

You are creating a KnockoutObservable for each element . Each of those elements are an individual Knockout Observable that can be listened to independently of each other. Just rather then having a property name to bind to, you have an array and key/index.

In 99% of cases, you are probably looking for an ObservableArray which is different.

Upvotes: 0

Ivan Mladenov
Ivan Mladenov

Reputation: 1847

When you subscribe to KnockoutObservable<string[]>, then you will receive a string array (string[])

The other one is an array of observables (KnockoutObservable<string>), each one resolving to a result with a type string.

When you wish to receive the string array, you should use KnockoutObservable<string[]>

Upvotes: 2

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