学步园

IE支持window.event， event.keyCode，event.returnValue

Firefox支持event.charCode ,event.preventDefault();

$amount.bind("keypress", function(event){
  if(window.event) {
   event = window.event;
   var keyCode = event.keyCode;
   if((keyCode >= 48 && keyCode <= 57) || keyCode == 46 || keyCode == 44) {
    return;
   }
   event.returnValue = false;
  } else {
   if(event.charCode === 0){
     return;
    }
    var char = String.fromCharCode(event.charCode);
    if((char === ".") ||
       (char === ",") ||
       (Number(char) >= 0)){
     return;
    }
    event.preventDefault();
  }   
  });