Changing Styles Dynamically

element.style.backgroundColor = 'blue';
element.style['background-color'] = 'blue';

Only camelCase syntax is valid
Only hyphenated syntax is valid
Both syntaxes are valid
Both camelCase and hyphenated syntaxes are valid when setting CSS properties in JavaScript using the style object. You can use either element.style.backgroundColor (camelCase) or element.style['background-color'] (hyphenated). The camelCase syntax is more commonly used as it follows JavaScript naming conventions, but the hyphenated syntax is useful when working with dynamic property names or CSS custom properties.
Neither syntax is valid