Category: JavaScript

Sometimes, we want to iterate over range in a functional way with JavaScript.

In this article, we’ll look at how to iterate over range in a functional way with JavaScript.

How to iterate over range in a functional way with JavaScript?

To iterate over range in a functional way with JavaScript, we use the array keys method.

For instance, we write

const arr = [...Array(20).keys()].map((i) => i * i);

to create an array with 20 empty slots with Array(20).

Then we call keys to return an array of indexes of the array.

And then we call map with a callback to map the index i to i squared.

Conclusion

To iterate over range in a functional way with JavaScript, we use the array keys method.

Sometimes, we want to check if a value is within a range of numbers with JavaScript.

In this article, we’ll look at how to check if a value is within a range of numbers with JavaScript.

How to check if a value is within a range of numbers with JavaScript?

To check if a value is within a range of numbers with JavaScript, we use comparison operators.

For instance, we write

const between = (x, min, max) => {
  return x >= min && x <= max;
};

if (between(x, 0.001, 0.009)) {
  // ...
}

to define the between function that checks if x is between min and max with

x >= min && x <= max

Conclusion

To check if a value is within a range of numbers with JavaScript, we use comparison operators.

Sometimes, we want to split a string into an array of characters with JavaScript

In this article, we’ll look at how to split a string into an array of characters with JavaScript.

How to split a string into an array of characters with JavaScript?

To split a string into an array of characters with JavaScript, we use the spread operator.

For instance, we write

const arr = [...str];

to spread the characters of the str string into an array.

This works properly with all Unicode characters.

Conclusion

To split a string into an array of characters with JavaScript, we use the spread operator.

Sometimes, we want to fix document.body null error with JavaScript.

In this article, we’ll look at how to fix document.body null error with JavaScript.

How to fix document.body null error with JavaScript?

To fix document.body null error with JavaScript, we should reference document.body only when the page is loaded.

For instance, we write

window.onload = () => {
  const mySpan = document.createElement("span");
  mySpan.innerHTML = "This is my span!";
  mySpan.style.color = "red";
  document.body.appendChild(mySpan);
};

to call document.body.appendChild in the window.onload method, which runs when the page is loaded.

If the page is loaded, that means the body element is loaded and document.body is available.

Conclusion

To fix document.body null error with JavaScript, we should reference document.body only when the page is loaded.