Efficient Javascript String Replacement

<div id='sample'>
  <h4>%TITLE%</h4>
  <p>Text text %KEYWORD% text</p>
  <p>%CONTENT%</p>
  <img src="images/%ID%/1.jpg" />
</div>

template = document.getElementById('sample');
template = template.replace(/%TITLE%/, some_var_with_title);
template = template.replace(/%KEYWORD%/, some_var_with_keyword);
template = template.replace(/%CONTENT%/, some_var_with_content);
template = template.replace(/%ID%/, some_var_with_id);

//Updated 28 October 2011: Now allows 0, NaN, false, null and undefined in output.
function template(templateid,data){
    return document.getElementById(templateid).innerHTML.replace(/%(w*)%/g,function(m,key){return data.hasOwnProperty(key)?data[key]:"";});
}

<div id="mytemplate">
  <p>%test%</p>
  <p>%word%</p>
</div>

document.getElementById("my").innerHTML=template("mytemplate",{test:"MYTEST",word:"MYWORD"});

var user = {
    "firstName": "John",
    "login": "john_doe",
    "password": "test",
};

var textbody = ""
+"Hey {firstName},n"
+"n"
+"You recently requested your password.n"
+"login: {login}n"
+"password: {password}n"
+"n"
+"If you did not request your password, please disregard this message.n"
+"";

textbody = textbody.replace(/{[^{}]+}/g, function(key){
    return user[key.replace(/[{}]+/g, "")] || "";
});

element.innerHTML = (new Template(element.innerHTML)).evaluate({
    title: 'a title',
    keyword: 'some keyword',
    content: 'A bunch of content',
    id: 'id here'
})

with(document.getElementById('sample'))
{
  innerHTML = innerHTML.replace(a, A).replace(b, B).replace(c, C); //etc
}