如何使用Javascript从输入框值获得总和？

Question

我在Javascript中并不完美.我想在名为total的下一个输入框中显示在qty输入框中输入的值的总和而不刷新页面.任何人都可以帮我弄清楚..？

这是javascript

 <script type="text/javascript"> 
 var howmanytoadd = 2;
 var rows;

 function calc() {
     var tot = 0;
     for (var i = 0; i < rows.length; i++) {
         var linetot = 0;
         rows[i].getElementsByTagName('input')[howmanytoadd].value = linetot;
         tot += linetot;
     }
     document.getElementById('total').value = tot
 }
 onload = function () {
     rows = document.getElementById('tab').getElementById('qty1');
     for (var i = 0; i < rows.length; i++) {
         rows.getElementsByTagName('input')[i].onkeyup = calc;
     }
 }
</script>

这是我的HTML代码:

Qty1 : <input type="text" name="qty1" id="qty"/><br>
Qty2 : <input type="text" name="qty2" id="qty"/><br>
Qty3 : <input type="text" name="qty3" id="qty"/><br>
Qty4 : <input type="text" name="qty4" id="qty"/><br>
Qty5 : <input type="text" name="qty5" id="qty"/><br>
Qty6 : <input type="text" name="qty6" id="qty"/><br>
Qty7 : <input type="text" name="qty7" id="qty"/><br>
Qty8 : <input type="text" name="qty8" id="qty"/><br>
<br><br>
Total : <input type="text" name="total" id="total"/>

这是屏幕截图

Answer 1

尝试:

Qty1 : <input onblur="findTotal()" type="text" name="qty" id="qty1"/><br>
Qty2 : <input onblur="findTotal()" type="text" name="qty" id="qty2"/><br>
Qty3 : <input onblur="findTotal()" type="text" name="qty" id="qty3"/><br>
Qty4 : <input onblur="findTotal()" type="text" name="qty" id="qty4"/><br>
Qty5 : <input onblur="findTotal()" type="text" name="qty" id="qty5"/><br>
Qty6 : <input onblur="findTotal()" type="text" name="qty" id="qty6"/><br>
Qty7 : <input onblur="findTotal()" type="text" name="qty" id="qty7"/><br>
Qty8 : <input onblur="findTotal()" type="text" name="qty" id="qty8"/><br>
<br><br>
Total : <input type="text" name="total" id="total"/>


    <script type="text/javascript">
function findTotal(){
    var arr = document.getElementsByName('qty');
    var tot=0;
    for(var i=0;i<arr.length;i++){
        if(parseInt(arr[i].value))
            tot += parseInt(arr[i].value);
    }
    document.getElementById('total').value = tot;
}

    </script>

Answer 2

$(document).ready(function(){

		//iterate through each textboxes and add keyup
		//handler to trigger sum event
		$(".txt").each(function() {

			$(this).keyup(function(){
				calculateSum();
			});
		});

	});

	function calculateSum() {

		var sum = 0;
		//iterate through each textboxes and add the values
		$(".txt").each(function() {

			//add only if the value is number
			if(!isNaN(this.value) && this.value.length!=0) {
				sum += parseFloat(this.value);
			}

		});
		//.toFixed() method will roundoff the final sum to 2 decimal places
		$("#sum").html(sum.toFixed(2));
	}

body {
				font-family: sans-serif;
			}
			#summation {
				font-size: 18px;
				font-weight: bold;
				color:#174C68;
			}
			.txt {
				background-color: #FEFFB0;
				font-weight: bold;
				text-align: right;
			}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>

<table width="300px" border="1" style="border-collapse:collapse;background-color:#E8DCFF">
	<tr>
		<td width="40px">1</td>
		<td>Butter</td>
		<td><input class="txt" type="text" name="txt"/></td>
	</tr>
	<tr>
		<td>2</td>
		<td>Cheese</td>
		<td><input class="txt" type="text" name="txt"/></td>
	</tr>
	<tr>
		<td>3</td>
		<td>Eggs</td>
		<td><input class="txt" type="text" name="txt"/></td>
	</tr>
	<tr>
		<td>4</td>
		<td>Milk</td>
		<td><input class="txt" type="text" name="txt"/></td>
	</tr>
	<tr>
		<td>5</td>
		<td>Bread</td>
		<td><input class="txt" type="text" name="txt"/></td>
	</tr>
	<tr>
		<td>6</td>
		<td>Soap</td>
		<td><input class="txt" type="text" name="txt"/></td>
	</tr>
	<tr id="summation">
		<td>&nbsp;</td>
		<td align="right">Sum :</td>
		<td align="center"><span id="sum">0</span></td>
	</tr>
</table>

Answer 3

使用Javascript:

window.sumInputs = function() {
    var inputs = document.getElementsByTagName('input'),
        result = document.getElementById('total'),
        sum = 0;            

    for(var i=0; i<inputs.length; i++) {
        var ip = inputs[i];

        if (ip.name && ip.name.indexOf("total") < 0) {
            sum += parseInt(ip.value) || 0;
        }

    }

    result.value = sum;
}?   

HTML:

Qty1 : <input type="text" name="qty1" id="qty"/><br>
Qty2 : <input type="text" name="qty2" id="qty"/><br>
Qty3 : <input type="text" name="qty3" id="qty"/><br>
Qty4 : <input type="text" name="qty4" id="qty"/><br>
Qty5 : <input type="text" name="qty5" id="qty"/><br>
Qty6 : <input type="text" name="qty6" id="qty"/><br
Qty7 : <input type="text" name="qty7" id="qty"/><br>
Qty8 : <input type="text" name="qty8" id="qty"/><br>
<br><br>
Total : <input type="text" name="total" id="total"/>

<a href="javascript:sumInputs()">Sum</a>

示例:http://jsfiddle.net/fRd9N/1/

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