html程式碼：

<div id="demo">
        <form action="">
            <input type="text" maxlength="3">
            <input type="text" maxlength="3">
            <input type="text" maxlength="3">
            <input type="text" maxlength="3">
            <input type=
 
"text" maxlength="3">
            <input type="text" maxlength="3">
        </form>
</div>

js程式碼：

var demo=document.getElementById('demo');
        input=demo.getElementsByTagName('input');
        var iNow=0;
        type   = !-[1,] ? 'onpropertychange' : 'oninput',
                limit  = 3
 
; //滿足自動切換焦點的字元數
        for(var i=0;i<input.length-1;i++){
            input[i].index=i;
            input[i][type]=function () {
                iNow=this.index;
                var that=this;
                setTimeout(function () {
                   that.value.length>limit-1&&input[iNow+1
 
].focus();
                },0)
            }
        }