Edit in JSFiddle

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();

<h1> Skype URI Scheme Browser Example:</h1>

<p>
Please change you username or use the default (echo123). The link actions will be automatically refreshed with the providen username:
</p>

<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>