js 实现自增长

   素材：  

      
        <
      
      
        script 
      
      
        type
      
      
        ="text/JavaScript">

function 
      
      qtyUpdate(kind){

    
      
        var 
      
      f = document.form1;

    
      
        var 
      
      c = f.qty.value;

    
      
        if
      
      (kind == 
      
        "up"
      
      ){

        c++;

    }
      
        else if
      
      (kind == 
      
        "down"
      
      ){

        
      
        if
      
      (c > 1) c--;

    }

    f.qty.value = c;

}


      
        </
      
      
        script
      
      
        >
      
    

      
        <
      
      
        FORM  
      
      
        name
      
      
        =form1 >

<
      
      
        TABLE 
      
      
        border
      
      
        =0 
      
      
        cellSpacing
      
      
        =0 
      
      
        cellPadding
      
      
        =0>

<
      
      
        TBODY
      
      
        >

<
      
      
        TR
      
      
        >

<
      
      
        TD 
      
      
        rowSpan
      
      
        =2><
      
      
        INPUT 
      
      
        value
      
      
        =2 
      
      
        readOnly size
      
      
        =5 
      
      
        name
      
      
        =qty></
      
      
        TD
      
      
        >

<
      
      
        TD 
      
      
        rowSpan
      
      
        =2 
      
      
        width
      
      
        =3></
      
      
        TD
      
      
        >

<
      
      
        TD
      
      
        ><
      
      
        A 
      
      
        href
      
      
        ="javascript:qtyUpdate('up')"><
      
      
        IMG 
      
      
        src
      
      
        ="btn_up.gif" 
      
      
        width
      
      
        =11 
      
      
        height
      
      
        =8></
      
      
        A
      
      
        ></
      
      
        TD
      
      
        >

</
      
      
        TR
      
      
        >

<
      
      
        TR
      
      
        >

<
      
      
        TD 
      
      
        align
      
      
        =right><
      
      
        A 
      
      
        href
      
      
        ="javascript:qtyUpdate('down')"><
      
      
        IMG 
      
      
        src
      
      
        ="btn_down.gif" 
      
      
        width
      
      
        =11 
      
      
        height
      
      
        =8></
      
      
        A
      
      
        ></
      
      
        TD
      
      
        >

</
      
      
        TR
      
      
        >

</
      
      
        TBODY
      
      
        >

</
      
      
        TABLE
      
      
        >

</
      
      
        FORM
      
      
        >