tryjsref_oper_plusequal 在线代码实例

 <p>x = 10 ， y = 5, 计算  x += y,  x 为:</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction() {
    var x = 10;
    var y = 5;
    x += y;
    document.getElementById("demo").innerHTML = x;
}
</script>