Category: JavaScript Answers

On many occasions, we want to create and style div elements in our web app dynamically.

In this article, we’ll look at how to create and style a div using JavaScript.

Using the document.createElement Method

We can create an HTML element using the document.createElement method.

To use it, we just pass in the tag name of the element we want to create as a string.

For instance, we can write:

const div = document.createElement("div");
div.style.width = "100px";
div.style.height = "100px";
div.style.background = "red";
div.style.color = "white";
div.innerHTML = "Hello";

document.body.appendChild(div);

to create a div, style it, and append it as the child of the body element.

createElement returns the element object.

Then we can set the properties of the style property to apply various styles.

All the CSS properties are in camel case in the style property.

innerHTML sets the content of the HTML element.

Set the innerHTML Property of document.body

We can also set the innerHTML property of document.body to a string with HTML code to add content to the body element.

For example, we can write:

const div = '<div>hello</div>';
document.body.innerHTML = div;

to set the innerHTML property of the div to what we want.

Conclusion

We can create a div by using the document.createElement method.

Then we can style it by assigning values to the properties of the style property.

Sometimes, we want to find the length of a JavaScript number in our JavaScript app.

In this article, we’ll look at how to find the length of a JavaScript number.

Convert the Number to a String and Use the String’s length Property

One way to find the length of a JavaSdcript number is to convert the number to a string and then use the string’s length property to get the number’s length.

For instance, we can write:

const x = 1234567;  
console.log(x.toString().length);

We have the number x .

Then we call toString on it to convert it to a string.

And then we use the length property to return its length.

Therefore, the console log should log 7.

Use the Math.ceil and Math.log Methods

We can get the logarithm of the number with base 10 to get the length of a number.

To do this, we cal use the Math.log to get the natural log of the number.

Then we can divide the returned result by Math.LN10 to convert it to the log with base 10 of the same number.

And then we call Math.ceil of that to round it up to the nearest integer to get the length.

For instance, we can write:

const x = 1234567;  
const len = Math.ceil(Math.log(x + 1) / Math.LN10);  
console.log(len);

to do all that.

We add 1 to x to avoid taking the log of 0 when x is 0.

Then we get that len is 7.

Use the Math.ceil and Math.log10 Methods

ES6 comes with the Math.log10 method to get the log with base 10 of a number.

To use it, we write:

const x = 1234567;  
const len = Math.ceil(Math.log10(x + 1));  
console.log(len);

We call Math.log10 with x + 1 to avoid taking the log of 0 when x is 0.

And we use Math.ceil again to round the log up to the nearest integer.

And so we should get the same result as the other examples.

Conclusion

We can find the length of a number with various JavaScript math methods or convert it to a string and use the length property.

Sometimes, we want to get the browser screen’s width with JavaScript code.

In this article, we’ll look at how to get a browser screen’s width with JavaScript code.

Using Properties of document.body or document.documentElement

The document.body is the JavaScript version of the HTML body element.

The document.documentElement is the JavaScript version of the HTML html element.

It has properties we need to get the width of the browser’s screen.

For instance, we can write:

const getWidth = () => {
  return Math.max(
    document.body.scrollWidth,
    document.documentElement.scrollWidth,
    document.body.offsetWidth,
    document.documentElement.offsetWidth,
    document.documentElement.clientWidth
  );
}

console.log(getWidth())

to create a function to get the width of the broiwser’s screen.

document.body.scrollWidth is the full width of the content of the body element.

document.documentElement.scrollWidth is the full width of the content of the html element.

document.body.offsetWidth is the width of the body element t.including any borders, padding, and vertical scrollbars.

document.documentElement.offsetWidth is the width of the html element t.including any borders, padding, and vertical scrollbars.

document.documentElement.clientWidth is the inner width of an element in pixels. It includes padding but excludes borders, margins, and vertical scrollbars of the html element.

Each of them is in pixels.

Therefore, we can use the Math.max method to get the max value between each of them.

The function should return a number with the max between all those values.

Conclusion

We can use various properties of document.body or document.documentElement to get the width of the screen.

Sometimes, we want to loop through a JavaScript associative array object in our JavaScript code.

In this article, we’ll look at how to loop through a JavaScript associative array object.

Use the for-in Loop

One way to loop through a JavaScript associative array object with the for-in loop.

For instance, we can write:

const obj = {
  a: 1,
  b: 2,
  c: 3
}
for (const key in obj) {
  const value = obj[key];
  console.log(key, value);
}

We create an obj object with some key-value pairs.

Then we loop through the object keys with the for-in loop.

We get the property value with obj[key] in the loop body.

Therefore, from the console log, we get:

a 1
b 2
c 3

Use the Object.entries with the forEach Method

We can use the Object.entries method to return an array of key-value pair arrays.

Then we can use the forEach method to loop through the array.

For instance, we can write:

const obj = {
  a: 1,
  b: 2,
  c: 3
}
Object.entries(obj).forEach(([key, value]) => console.log(key, value));

We call forEach with a callback with an array with the key and value destructured from it.

Then in the callback body, we log the key and value .

Therefore, we get the same result as before.

Use the for-of Loop

Another way to loop through the key-value pairs is to use the for-of loop.

For example, we can write:

const obj = {
  a: 1,
  b: 2,
  c: 3
}

for (const [key, value] of Object.entries(obj)) {
  console.log(key, value)
}

We use Object.entries to return an array of key-value pair arrays.

And we destructure the key and value from the destructured key-value arrays.

And we log the key and value from the console log.

Conclusion

There’re several ways we can use to loop through the key-value pair of an associative array object with JavaScript.

Sometimes, we want to remove a leading comma from a JavaScript string.

In this article, we’ll look at how to remove a leading comma from a JavaScript string.

Using the String.prototype.substring Method

We can use the JavaScript string substring method to get the part of a string.

Therefore, we can use it to return a string without the leading comma.

For instance, we can write:

const myOriginalString = ",'first string','more','even more'";
const newString = myOriginalString.substring(1);
console.log(newString)

We call substring with 1 to return a string the part of myOriginalString from index 1 to the end.

Therefore, newString is "’first string’,’more’,’even more’” .

Using the String.prototype.split Method

We can use the JavaScript string split method to split a string by a separator string.

For instance, we can write:

const myOriginalString = ",'first string','more','even more'";
const [_, ...rest] = myOriginalString.split(',');
const newString = rest.join(',')
console.log(newString)

We call split with ',' to split myOriginalString by the comma.

Then we use the rest operator to get a string array with anything but the first comma.

And then we call join with ',' to join the strings in rest with the comma.

And so newString has the same value as before.

Using the String.prototype.replace Method

Another way to remove the leading commas from a string is to use the JavaScript string’s replace method.

For example, we can write:

const myOriginalString = ",'first string','more','even more'";
const newString = myOriginalString.replace(/^,/, '');
console.log(newString)

We call replace with /^,/ to replace the leading comma with an empty string.

And so newString is the same as before.

Conclusion

We can use various string methods to get rid of the leading comma from a string.