Получение элементов по названию класса

let blueThings = document.getElementsByClassName('blue');

console.log(blueThings);                        // The HTMLCollection
console.log(blueThings[0]);                     // The first element with class="blue" in the document
console.log(blueThings.length);                 // The number of elements with class="blue" found
console.log(blueThings.item(2));                // The element at index 2 in the collection
console.log(blueThings.namedItem('specific'));  // The element with both class="blue" and id="specific"
Gorgeous Goldfinch