Máscara para CNPJ

maskCnpj.js

const inputCnpj = document.querySelector('.cnpj input');

function handleInputCnpj() {
		let value = inputCnpj.value.replace(/\D/g, '');
		let mask = '';

		if (value.length <= 2) {
			mask = value;
		} else if (value.length <= 5) {
			mask = value.slice(0, 2) + '.' + value.slice(2);
		} else if (value.length <= 8) {
			mask = value.slice(0, 2) + '.' + value.slice(2, 5) + '.' + value.slice(5);
		} else if (value.length <= 12) {
			mask = value.slice(0, 2) + '.' + value.slice(2, 5) + '.' + value.slice(5, 8) + '/' + value.slice(8);
		} else {
			mask = value.slice(0, 2) + '.' + value.slice(2, 5) + '.' + value.slice(5, 8) + '/' + value.slice(8, 12) + '-' + value.slice(12);
		}

		inputCnpj.value = mask;
	}	

inputCnpj.addEventListener('input', handleInputCnpj);