const source = document.getElementById('source');
source.addEventListener('input', allowOnlyNumberAndDecimals);
function allowOnlyNumberAndDecimals(e) {
let str = e.target.value
const regExp = /^(d+(.d+)?)$/
let status = regExp.test(str) ? 'valid' : 'invalid'
console.log(status + ' : ' + source.value)
}