tryjs_function_counter 在线代码实例

 <p>全局变量计数。</p>
<button type="button" onclick="myFunction()">计数!</button>
<p id="demo">0</p>
<script>
var counter = 0;
function add() {
    return counter += 1;
}
function myFunction(){
    document.getElementById("demo").innerHTML = add();
}
</script>