js 之 复制一段代码

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
.kcont {
    border: 1px solid #ccc;
    background-color: #D2E9FF;
    position:relative;
    height:300px;
    font-size:16px;
}
.area { width:99%; background:none; border:none; display:block; font-size:16px;}
</style>
</head>

<body>
<div class="kcont" id="cont">
<p>
复制我！！！！！！！！</p>
function trim(str){ <br />
str = str.replace(/^(\s|\u00A0)+/,''); <br />
for(var i=str.length-1; i&gt;=0; i--){ <br />
if(/\S/.test(str.charAt(i))){ <br />
str = str.substring(0, i+1); <br />
break; <br />
} <br />
} <br />
return str; <br />
}
</p>
<form id="form"><input type="submit" name="button" id="button" value="复制" /></form>
</div>

<script>
var but = document.getElementById("button");
but.addEventListener("click",copy);

Selection = function(input){
        this.isTA = (this.input = input).nodeName.toLowerCase() == "textarea";
};
with({o: Selection.prototype}){
        o.setCaret = function(start, end){
                var o = this.input;
                if(Selection.isStandard)
                        o.setSelectionRange(start, end);
                else if(Selection.isSupported){
                        var t = this.input.createTextRange();
                        end -= start + o.value.slice(start + 1, end).split("\n").length - 1;
                        start -= o.value.slice(0, start).split("\n").length - 1;
                        t.move("character", start), t.moveEnd("character", end), t.select();
                }
        };
        o.getCaret = function(){
                var o = this.input, d = document;
                if(Selection.isStandard)
                        return {start: o.selectionStart, end: o.selectionEnd};
                else if(Selection.isSupported){
                        var s = (this.input.focus(), d.selection.createRange()), r, start, end, value;
                        if(s.parentElement() != o)
                                return {start: 0, end: 0};
                        if(this.isTA ? (r = s.duplicate()).moveToElementText(o) : r = o.createTextRange(), !this.isTA)
                                return r.setEndPoint("EndToStart", s), {start: r.text.length, end: r.text.length + s.text.length};
                        for(var $ = "[###]"; (value = o.value).indexOf($) + 1; $ += $);
                        r.setEndPoint("StartToEnd", s), r.text = $ + r.text, end = o.value.indexOf($);
                        s.text = $, start = o.value.indexOf($);
                        if(d.execCommand && d.queryCommandSupported("Undo"))
                                for(r = 3; --r; d.execCommand("Undo"));
                        return o.value = value, this.setCaret(start, end), {start: start, end: end};
                }
                return {start: 0, end: 0};
        };
        o.getText = function(){
                var o = this.getCaret();
                return this.input.value.slice(o.start, o.end);
        };
        o.setText = function(text){
                var o = this.getCaret(), i = this.input, s = i.value;
                i.value = s.slice(0, o.start) + text + s.slice(o.end);
                this.setCaret(o.start += text.length, o.start);
        };
        new function(){
                var d = document, o = d.createElement("input"), s = Selection;
                s.isStandard = "selectionStart" in o;
                s.isSupported = s.isStandard || (o = d.selection) && !!o.createRange();
        };
}

function copy (){

    var cont = document.getElementById("cont");
    var ele = document.createElement("textarea");
    ele.style.height = cont.offsetHeight+"px"
    ele.className = "area"; ele.id = "area";
    ele.innerHTML = cont.innerText ;
    cont.innerHTML = "";
    cont.appendChild(ele);

    var le = document.getElementById("area");
    var selection = new Selection(le);
    selection.setCaret(0,le.value.length);
    le.focus();

}
</script>
</body>
</html>