Edit in JSFiddle

var num = 0;

$(function () {
    function appendit (cl) {
        num++;
		var div = document.createElement("div");
		var txt = document.createTextNode("append-"+num);
		div.appendChild(txt);
        div.setAttribute("class", cl);
		var wrapper = document.getElementById("wrapper");
		wrapper.appendChild(div);
    }
    var appendit_once = _.once(appendit);
    $(".trigger").click(function(){
        var cl = $(this).attr("class");
        appendit(cl);
    });
    $(".trigger2").click(function(){
        var cl = $(this).attr("class");
        appendit_once(cl);
    });
    
});

<p>_.once Practice</p>
<div id="wrapper">
    <a href="#" class="trigger" >何回でも発動</a>
    <a href="#" class="trigger2" >一回だけ発動</a>
</div>

p, div {
    margin: 20px 20px 0px;
    clear:both;
}

div.trigger2{
    color:red;
}