Scale a text to fit inside of an element

<div id="headline">Hello World</div>

const measureWidth = function(text, font) {
    // Measure the width of given text for given font
    ...
};

// Query the element
const ele = document.getElementById('headline');

// Get the styles
const styles = window.getComputedStyle(ele);

// Get the font size and font style
const font = styles.font;
const fontSize = parseInt(styles.fontSize);

const measured = measureWidth(ele.textContent, font);

const scale = ele.clientWidth / parseFloat(measured);

const scaleFontSize = Math.floor(scale * fontSize);
ele.style.fontSize = `${scaleFontSize}px`;