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How to change root font in ReactJS


Change is a fundamental part of life and it is no different in the world of programming. ReactJS, a popular JavaScript library used for building user interfaces, is highly flexible and allows you to change many aspects of your application, including the root font. In this blog post, we are going to explore how.

Understanding the Concept of Root Font

Before we dive into the 'how', let's first understand the 'what'. What is a root font? The root font is the base font size that all other relative font sizes are calculated from. In the world of CSS, the root element is typically the <html> tag and the font size of this root element is the root font.

Think of it as the "mother font" from which all other "child fonts" derive their sizes. This enables a form of inheritance, where child elements can have font sizes relative to the parent, creating a nice, scalable system for font sizes.

How ReactJS Deals with Styles

Now that we know what a root font is, let's see how ReactJS deals with it. Unlike traditional HTML and CSS where you'd define styles in a separate CSS file, in ReactJS, you can define these styles directly inside your JavaScript code using a concept called inline styles.

Inline styles in ReactJS are written as JavaScript objects where CSS property names become keys and CSS values become values. For example, instead of writing font-size: 16px; in CSS, in ReactJS, we would write fontSize: '16px'.

Changing the Root Font in ReactJS

So, how do we change the root font in ReactJS? Let's break it down step-by-step.

Step 1: Create a Style Object

First, we need to create a style object with our desired root font size. Let's say we want our root font size to be 18px. Here's how we can define it:

const rootFontStyle = {
    fontSize: '18px'

Step 2: Apply the Style to the Root Element

Next, we need to apply this style to our root element. In a ReactJS application, the root element is typically the element where your app is mounted, often an element with the id of 'root'. Here's how we can apply the style:

    <div style={rootFontStyle}>
        <App />

In the code above, we are wrapping our <App /> component with a <div> and applying our rootFontStyle to it. This div element essentially becomes our root element and all child elements inside it will now use this font size as their base.

Understanding the Impact

By setting the root font size, we are setting a baseline for all other font sizes in our application. If we use relative units like em or rem for our other font sizes, they will now be calculated based on this root font size.

For example, if we have a style like this:

const headingStyle = {
    fontSize: '2em'

The font size of elements with this style will be twice the root font size, or 36px in our case.


In essence, changing the root font in ReactJS is like adjusting the tuner on a musical instrument. Just as the tuner sets the pitch for all the notes, the root font sets the base size for all the fonts in your application. It allows for a harmonious, scalable system of font sizes that can make your app more accessible and easier to style. So go ahead and play around with it, tune your application to your liking and make some beautiful (web) music!