<html>
<body>
<p>该实例中，我们忽略了最后一个参数，在循环体中执行递增。</p>
<p>点击按钮以索引(升序)的方式循环数组。</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction() {
var cars = ["BMW", "Volvo", "Saab", "Ford"];
var i = 0;
var len = cars.length;
var text = "";
for (; i < len;) {
text += cars[i] + "<br>";
i++;
}
document.getElementById("demo").innerHTML = text;
}
</script>
</body>
</html>