javascript禁止输入数字

 function onkeypressIsNumber(){
     var mainForm = document.mainForm;//mainForm是form表单的ID
     for(var i=0; i<mainForm.elements.length; i++){
         if(mainForm.elements[i].type == "text"){
             var element = mainForm.elements[i];
             element.onkeypress = function(element){
                 var charCode = (element.which) ? element.which : event.keyCode;
                 if (charCode > 31 && (charCode < 48 || charCode > 57) && charCode != 46) {
                      return false;
                 }
                 return true;
             }
         }
     }
 }