Here's an ES6 version of the answer provided by 7stud.
const sel = document.createElement('select');
sel.name = 'drop1';
sel.id = 'Select1';
const cars = [
"Volvo",
"Saab",
"Mercedes",
"Audi",
];
const options = cars.map(car => {
const value = car.toLowerCase();
return `<option value="${value}">${car}</option>`;
});
sel.innerHTML = options;
window.onload = () => document.body.appendChild(sel);