Category: JavaScript Answers

Sometimes, we want to to call finally on subscribing to observable with Rxjs and JavaScript.

In this article, we’ll look at how to to call finally on subscribing to observable with Rxjs and JavaScript.

How to call finally on subscribing to observable with Rxjs and JavaScript?

To to call finally on subscribing to observable with Rxjs and JavaScript, we call pipe on the observable we subscribed to.

For instance, we write

const source = new Observable((observer) => {
  observer.next(1);
  observer.error("error message");
  observer.next(3);
  observer.complete();
}).pipe(publish());

source.pipe(finalize(() => console.log("Finally callback"))).subscribe(
  (value) => console.log(value),
  (error) => console.log(error),
  () => console.log("complete")
);

to create an Observable.

And then we call pipe to emit the data.

Then we call pipe with the observable returned by finalize.

We call finalize with a callback that runs when all the observable code is run.

pipe returns another observable that we call subscribe on to get the data from pipe.

Conclusion

To to call finally on subscribing to observable with Rxjs and JavaScript, we call pipe on the observable we subscribed to.

Sometimes, we want to remove whitespaces inside a string in JavaScript.

In this article, we’ll look at how to remove whitespaces inside a string in JavaScript.

How to remove whitespaces inside a string in JavaScript?

To remove whitespaces inside a string in JavaScript, we can call the string replace method.

For instance, we write

const s = "hello world".replace(/\s/g, "");

to call replace with /\s/g and '' to replace all whitespaces with empty strings.

We use \s to match whitespaces.

g makes replace do the replacement on all matches.

Conclusion

To remove whitespaces inside a string in JavaScript, we can call the string replace method.

Sometimes, we want to simulate a mouse click using JavaScript.

In this article, we’ll look at how to simulate a mouse click using JavaScript.

How to simulate a mouse click using JavaScript?

To simulate a mouse click using JavaScript, we can use the MouseEvent constructor.

For instance, we write

const evt = new MouseEvent("click", {
  view: window,
  bubbles: true,
  cancelable: true,
  clientX: 20,
  //...
});
targetElement.dispatchEvent(evt);

to create a MouseEvent object with 'click' and an object with the event object options.

We set the view to the page where the mouse event is triggered.

Also, we set whether the event bubbles and if it’s cancelable.

We can also set the location of the click.

Then we trigger the event with

targetElement.dispatchEvent(evt);

from the targetElement element.

Conclusion

To simulate a mouse click using JavaScript, we can use the MouseEvent constructor.

Sometimes, we want to find index of all occurrences of element in array with JavaScript.

In this article, we’ll look at how to find index of all occurrences of element in array with JavaScript.

How to find index of all occurrences of element in array with JavaScript?

To find index of all occurrences of element in array with JavaScript, we use the array map method.

For instance, we write

const indices = array.map((e, i) => (e === value ? i : "")).filter(String);

to call map with a callback that checks if array entry e is equal to value.

If it is, we return i.

Otherwise, we return an empty string.

And we call filter with String to filter out all the empty strings since they’re falsy.

Conclusion

To find index of all occurrences of element in array with JavaScript, we use the array map method.

Sometimes, we want to run JavaScript code on window close or page refresh.

In this article, we’ll look at how to run JavaScript code on window close or page refresh.

How to run JavaScript code on window close or page refresh?

To run JavaScript code on window close or page refresh, we add an event handler for the beforeunload event.

For instance, we write

window.onbeforeunload = () => {
  // Do something
};

to set the window.onbeforeunload property to a function that runs when the window closes or the page refreshes.

Conclusion

To run JavaScript code on window close or page refresh, we add an event handler for the beforeunload event.