Category: JavaScript Answers

Sometimes, we want to stop a web page from scrolling to the top when a link is clicked that triggers JavaScript.

In this article, we’ll look at how to stop a web page from scrolling to the top when a link is clicked that triggers JavaScript.

How to stop a web page from scrolling to the top when a link is clicked that triggers JavaScript?

To stop a web page from scrolling to the top when a link is clicked that triggers JavaScript, we call preventDefault in the link’s click handler.

For instance, we write

document.getElementById("#ma_link").addEventListener("click", (e) => {
  e.preventDefault();
  doSomething();
});

to select the link with getElementById.

Then we call addEventListener with 'click' and a click event handler callback.

In the callback, we call e.preventDefault to stop the default behavior of scrolling to the top of the page when the link is clicked.

Conclusion

To stop a web page from scrolling to the top when a link is clicked that triggers JavaScript, we call preventDefault in the link’s click handler.

Sometimes, we want to compute the cartesian product of multiple arrays in JavaScript.

In this article, we’ll look at how to compute the cartesian product of multiple arrays in JavaScript.

How to compute the cartesian product of multiple arrays in JavaScript?

To compute the cartesian product of multiple arrays in JavaScript, we can use the array flatMap and reduce methods.

For instance, we write

const data = [
  [1, 2],
  [10, 20],
  [100, 200, 300],
];
const prod = data.reduce(
  (a, b) => a.flatMap((x) => b.map((y) => [...x, y])),
  [[]]
);

to call data.reduce with a callback that calls a.flatMap with a callback that calls b.map with a callback to spread the entries of x and y in a new array and returns it.

This will get the entries from each array and put them in the nested arrays will do this for all combinations of entries for all arrays.

Conclusion

To compute the cartesian product of multiple arrays in JavaScript, we can use the array flatMap and reduce methods.

Sometimes, we want to add the JavaScript equivalent of Python ‘enumerate’ for a sequence.

In this article, we’ll look at how to add the JavaScript equivalent of Python ‘enumerate’ for a sequence.

How to add the JavaScript equivalent of Python ‘enumerate’ for a sequence?

To add the JavaScript equivalent of Python ‘enumerate’ for a sequence, we call the array entries method.

For instance, we write

const foobar = ["A", "B", "C"];

for (const [index, element] of foobar.entries()) {
  console.log(index, element);
}

to call foobar.entries to return an array with arrays of the index and element value for each entry.

index has the array entry index.

And element has the element at the index.

Conclusion

To add the JavaScript equivalent of Python ‘enumerate’ for a sequence, we call the array entries method.

Sometimes, we want to get HTML a tag work with href and onclick with JavaScript.

In this article, we’ll look at how to get HTML a tag work with href and onclick with JavaScript.

How to get HTML a tag working with href and onclick with JavaScript?

To get HTML a tag work with href and onclick with JavaScript, we can handle the navigation and clicks with the click handler.

For instance, we write

<a id="myButton" href="http://example.com">Click me!</a>

to add a link.

Then we write

document.querySelector("#myButton").addEventListener("click", (e) => {
  e.preventDefault();
  window.location = e.target.href;
});

to select the link with querySelector.

And we call addEventListener with 'click' and the click event handler callback.

In it, we call preventDefault to prevent the default navigation behavior of going to the URL set as the href attribute value.

And then we go to the href URL with

window.location = e.target.href

Conclusion

To get HTML a tag work with href and onclick with JavaScript, we can handle the navigation and clicks with the click handler.

Sometimes, we want to compare JavaScript sets for equality.

In this article, we’ll look at how to compare JavaScript sets for equality.

How to compare JavaScript sets for equality?

To compare JavaScript sets for equality, we can check if 2 sets have all the same entries and have the same size.

For instance, we write

const a = new Set([1, 2, 3]);
const b = new Set([1, 3, 2]);

const areSetsEqual = (a, b) =>
  a.size === b.size && [...a].every((value) => b.has(value));

console.log(areSetsEqual(a, b));

to create 2 sets a and b.

And then we check if both sets are equal with the areSetEqual function.

In it, we check if both have the same size with

a.size === b.size 

Then we convert a to an array with the spread operator and call every on the array with a callback that check if a has all the same entries as b with has.

If they have the same size and the same entries, then they’re the same since sets can’t have duplicate values.

Conclusion

To compare JavaScript sets for equality, we can check if 2 sets have all the same entries and have the same size.