The cssText property allows you to set multiple CSS styles for an element in one line at once. This is useful when you need to quickly apply multiple styles without using separate properties of the style object.

element.style.cssText = 'rule1; rule2; ...';

A real code example for applying multiple styles

let box = document.getElementById('myBox');
box.style.cssText = 'width: 200px; height: 100px; background: black;';

An example of adding new styles without deleting the old ones

box.style.cssText += 'border: 2px solid black;';

If you refer to cssText, it will return the data as a string

console.log(box.style.cssText); 
// "width: 200px; height: 100px; background: black;"

If you want to add styles without overwriting existing ones, it is better to use classList.add() to work with classes or separate style properties.

cssText is a fast way to apply styles en masse, but you need to be careful with it: it removes all previous inline styles. If the style of the element changes dynamically, it is better to use style.property or classes.