使文本框只能输入数字

 <input    onkeyup="this.value=this.value.replace(/\D/g,'')"    onafterpaste="this.value=this.value.replace(/\D/g,'')">      
 
or  
   
<input    name=txt1    onchange="if(/\D/.test(this.value)){alert('只能输入数字');this.value='';}">      
 
or  
   
<input    onkeyup="if(isNaN(value))execCommand('undo')"    onafterpaste="if(isNaN(value))execCommand('undo')">