javascript两个参数无刷新相乘

Question

javascript两个参数无刷新相乘，在文本框里输入一个数结果就会发生变化

Answer 1

<input id="txt1" type="text" size=5 onkeyup="document.getElementById('span').innerText=eval(this.value)*eval(document.getElementById('txt2').value)"/> *
<input id="txt2" type="text" size=5 onkeyup="document.getElementById('span').innerText=eval(this.value)*eval(document.getElementById('txt1').value)"/>
<span id="span"/>

Answer 2

 <script type="text/javascript">
        function ic() {
            alert(document.getElementById("Num1").value * document.getElementById("Num2").value);
        }
    </script> <input type="text" id="Num1" />
    <input type="text" id="Num2" onblur="ic();" />
弹出结果

Answer 3

function getNum() {
            var firstStr = document.getElementById("Num1").value;
            var SccondStr = document.getElementById("Num2").value;
            var Num;
            if (parseInt(firstStr) && parseInt(SccondStr)) {
                Num = firstStr * SccondStr;
                alert(Num);
            }
            else {
                alert("请输入数字！")
            }
        }