Get a style, and then if this style is not set as an inline style directly on the element, it returns an empty string.
var elem = document.querySelector('#sandwich');
// Get a style
// If this style is not set as an inline style directly on the element, it returns an empty string
// ex. <div id="sandwich" style="background-color: green"></div>
var bgColor = elem.style.backgroundColor; // this will return "green"
var fontWeight = elem.style.fontWeight; // this will return ""
// Set a style
elem.style.backgroundColor = 'purple';