JS判断输入框是否是正确的车牌号码，只能是大写字母数字组成，并规定格式
js方法
//失去车牌号码焦点弹出function lostBlur(){var charsets="ABCDEFGHIJKLMNOPQRSTUVWXYZ";var smallchat = "abcdefghijklmnopqrstuvwxyz";var num="0123456789";var one = form.carNumber.value;//输入text值var oneString = one.substring(0,1);var twoString; var a=0;var j=0;var b=0;var c=0;for(var i=0;i<5;i++){twoString = one.substring(i+1,i+2);if(num.indexOf(twoString)>=0){j++;//数字个数}elseif(charsets.indexOf(twoString)>=0){a++;//大写字母个数}else if(smallchat.indexOf(twoString)>=0){b++;//小写}if(twoString==" "){ c++;//空格}}if(one!=""){if(one.length==6){//车牌号码为6位if(c==0){if(charsets.indexOf(oneString)!=-1){if(a!=5){if(b<=0){}else{alert("不能有小写字母");}}else{alert("不能全是字母");}}else{alert("首位应该是大写字母");}}else{ alert("你输入的含有空格");}}else{alert("号牌号码应为6位");}}else{alert("请填写完整的车牌号码信息");}}<input name="carNumber" type="text" id="12" onblur="lostBlur();">