I have used regular expression to replace the input value with the pattern needed.
var userName = document.querySelector('#numberField');_x000D_
_x000D_
userName.addEventListener('input', restrictNumber);_x000D_
function restrictNumber (e) { _x000D_
var newValue = this.value.replace(new RegExp(/[^\d]/,'ig'), "");_x000D_
this.value = newValue;_x000D_
}_x000D_
_x000D_
<input type="text" id="numberField">
_x000D_