?document.getElementById("fruit")value=jieguo; ? value后面少個(gè). ? ? ?

<input type='button' value=' = ' onclick="count()"/>

value中寫(xiě)規(guī)范一些，雙引號(hào)中最好不要有空格

?document.getElementById("fruit")value=jieguo;?????? 差了一個(gè)點(diǎn)，就是document.getElementById("fruit").value=jieguo;?

document.getElementById("fruit").value=jieguo;

應(yīng)寫(xiě)在function之外

? <script type="text/javascript">

? ?function count(){

var txt1 ? = parseInt( document.getElementById('txt1').value);//獲取第一個(gè)輸入框的值

var txt2 ? = parseInt( document.getElementById('txt2').value);//獲取第二個(gè)輸入框的值

var select = document.getElementById('select').value;//獲取選擇框的值

var result = '';

switch (select)

{

case '+':

result = txt1 + txt2;

break;

case '-':

result = txt1 - txt2;

break;

case '*':

result = txt1 * txt2;

break;

case '/':

result = txt1 / txt2;

break; ?

}

? ? ? ? ?document.getElementById('fruit').value = result;//設(shè)置結(jié)果輸入框的值?

? ?}

? </script>?