prevent from pressing digits without alphabets and spaces

jQuery, keypress, e.preventDefault(),e.charCode, e.which

HTML

<input id="inputTextBox" type="text" />

JavaScript

$(document).ready(function(){
    $("#inputTextBox").keypress(function(event){
        var inputValue = event.charCode;
        if(!(inputValue >= 65 && inputValue <= 120) && (inputValue != 32 && inputValue != 0)){
            event.preventDefault();
        }
    });
});