1
<p id="demo">点击按钮截取字符串。</p>2
<button onclick="myFunction()">点我</button>3
<script>4
function myFunction() {5
var str = "Hello world!";6
var n = str.substr(2, 3);7
document.getElementById("demo").innerHTML = n;8
}9
</script>
<p id="demo">点击按钮截取字符串。</p><button onclick="myFunction()">点我</button><script> function myFunction() { var str = "Hello world!"; var n = str.substr(2, 3); document.getElementById("demo").innerHTML = n; }</script>