console.log(work([-10, -20, -40])); // -40 - (-10) = -30 => 30
const arr = [-10, -20, -40];
const calcDifference = (array) => Math.max(...array) - Math.min(...array);
console.log(calcDifference(arr)); // 30
.header .nav-menu .nav-list__item:last-child
.header .nav-menu .nav-list
.header .nav-menu .nav-list__link
Из документации Magnific Popup