我試圖使用Skype與HTML和爪哇腳本進行聊天。這里的問題是我無法將屬性href添加到我的id中。這里我的代碼：function el(elementId, username, action) {    document.getElementById(elementId).setAttribute("href", "skype:" + username + "?" + action);}function buildLinkRefs() {    var username = document.getElementById("username").value;    el("call-btn", username, "call");    el("add-to-contacts-btn", username, "add");    el("view-profile-btn", username, "userinfo");    el("voice-email-btn", username, "voicemail");    el("chat-btn", username, "chat");    el("sendfile-btn", username, "sendfile");}document.getElementById("username").addEventListener("change", function () {    buildLinkRefs();}, false);buildLinkRefs();            <input type="text" id="username" value="echo123"/><br>    <br>    <a id="call-btn">Call</a> <br>    <a id="add-to-contacts-btn">Add to contacts</a> <br>    <a id="view-profile-btn">View User Profile</a> <br>    <a id="voice-email-btn">Voice Email</a> <br>    <a id="chat-btn">Start Chat</a> <br>    <a id="sendfile-btn">Send File</a> <br>