< input type = text >< input type = text value = " 这个有字 " >< input type = text > < Script > var str1 = document.all.tags( " INPUT " ) for (i = 0 ;i < str1.length;i ++ ) {if(str1[i].type=="text"&&str1[i].value==""){alert("你必须在第"+(i+1)+"个输入框中输入内容");str1[i].focus();}} </ script >