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In this lecture, we are going to start using operators to help us write observables.

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We're going to focus on creation operators for the next couple of lectures.

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As a refresher, a creation operator is a function for creating an observable.

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It will act as a wrapper around a producer of data such as events, timers or a combination of other

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observables creation.

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Operators make it possible to create observables from any source of data.

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We will be exploring the most commonly used operators in our jobs.

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The first operator we're going to explore is called the interval operator inside our code.

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We're manually creating an interval with the set interval function.

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Writing an observable from scratch is tedious.

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We can simplify it with the interval operator at the top of the file.

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We're going to update the important statement for the SJS package instead of importing the observable

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class.

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We will import an operator called Interval.

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Next, we will completely replace the instance of the observable class with the interval operator.

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The interval operator will perform a couple of tasks.

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Firstly, it'll create an interval similar to these set interval function.

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This interval will be wrapped with an observable.

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The observable is returned as a value.

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We can verify the return value by hovering our mouse over the interval function.

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The return value of this function is annotated as an observable with a single function.

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We will accomplish the same solution we had previously.

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We've gone from an imperative solution to a declarative solution.

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The interval operator will emit a stream of values based on the duration passed into the function.

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That aeration must be in milliseconds.

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Let's pass in one thousand.

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By default, intervals will limit numbers in ascending order.

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If we look inside the console, the numbers start at zero.

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Going up to four, the interval stops because we're unsubscribing from the observable after four seconds.

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It's worth mentioning the interval will go on forever.

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It never completes.

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Let's remove the set timeout function altogether.

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As you can see, the observable will continue to emit values.

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We can simplify our code even further.

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At the moment, we're passing in an object.

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Alternatively, we can pass in a single function, passing at a single function to the subscribe function.

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It will be registered as the next function.

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This shorthand syntax for creating an observer it can be useful if you're not concerned with completing

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an observable or its errors.

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Let's replace the object with the console log function.

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Everything has become much more readable.

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Back to the task at hand.

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The interval operator can be helpful if you need to create a countdown or delay an event.

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There are some limitations with the interval operator.

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It'll continuously emit values.

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However, we may want to emit one value.

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Secondly, we may want to emit a value immediately without delay for subsequent values.

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There's another operator with more options for customizing the interval in our file.

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Let's swap the interval operator with the timer operator.

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The timer operator offers more flexibility than the interval operator.

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They're very similar.

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Just like the interval operator, the timer operator will emit a stream of numbers to the observer inside

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the console.

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A single number has been emitted.

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The first argument of the timer operator is a timer for the first value it emits.

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We can configure when the interval should begin.

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In this example, we are starting the interval after one seconds if we want to begin emitting values

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immediately.

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We can pass in zero.

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The timer operator will emit one value we can emit values in intervals by passing in a duration as the

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second argument to the function by omitting the second argument.

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The timer operator will assume we want to emit a single value.

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Let's pass in one thousand.

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This time, the operator is emitting values every second, the duration in the second argument applies

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to subsequent values.

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It does not apply to the first value emitted by the observable with the timer operator.

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We can fine tune the delay of each value.

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In general, it's not necessary to manually create an observable.

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Our SJS is a powerful library packed with numerous operators to help us create observables we can jumpstart

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in observable with a single operator in the next lecture.

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We will continue learning about creation operators.