Insertion de balises dans une zone de texte

<textarea onkeyup="preview(this, 'previewDiv');" ...

function preview(textareaId, previewDiv) {
	var field = textareaId.value;
	if (document.getElementById('previsualisation').checked && field) {
		
		var smiliesName = new Array(':magicien:', ':colere:', ':diable:', ':ange:', ':ninja:', '>_<', ':pirate:', ':zorro:', ':honte:', ':soleil:', ':\'\\(', ':waw:', ':\\)', ':D', ';\\)', ':p', ':lol:', ':euh:', ':\\(', ':o', ':colere2:', 'o_O', '\\^\\^', ':\\-°');
		var smiliesUrl  = new Array('magicien.png', 'angry.gif', 'diable.png', 'ange.png', 'ninja.png', 'pinch.png', 'pirate.png', 'zorro.png', 'rouge.png', 'soleil.png', 'pleure.png', 'waw.png', 'smile.png', 'heureux.png', 'clin.png', 'langue.png', 'rire.gif', 'unsure.gif', 'triste.png', 'huh.png', 'mechant.png', 'blink.gif', 'hihi.png', 'siffle.png');
		var smiliesPath = "http://www.siteduzero.com/Templates/images/smilies/";
	
		field = field.replace(/&/g, '&amp;');
		field = field.replace(/</g, '<').replace(/>/g, '>');
		field = field.replace(/\n/g, '<br />').replace(/\t/g, '&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;');
		
		field = field.replace(/([\s\S]*?)<\/gras>/g, '<strong>$1</strong>');
		field = field.replace(/<italique>([\s\S]*?)<\/italique>/g, '<em>$1</em>');
		field = field.replace(/<lien>([\s\S]*?)<\/lien>/g, '<a href="$1">$1</a>');
		field = field.replace(/<lien url="([\s\S]*?)">([\s\S]*?)<\/lien>/g, '<a href="$1" title="$2">$2</a>');
		field = field.replace(/<image>([\s\S]*?)<\/image>/g, '<img src="$1" alt="Image" />');
		field = field.replace(/<citation nom=\"(.*?)\">([\s\S]*?)<\/citation>/g, '<br /><span class="citation">Citation : $1</span><div class="citation2">$2</div>');
		field = field.replace(/<citation lien=\"(.*?)\">([\s\S]*?)<\/citation>/g, '<br /><span class="citation"><a href="$1">Citation</a></span><div class="citation2">$2</div>');
		field = field.replace(/<citation nom=\"(.*?)\" lien=\"(.*?)\">([\s\S]*?)<\/citation>/g, '<br /><span class="citation"><a href="$2">Citation : $1</a></span><div class="citation2">$3</div>');
		field = field.replace(/<citation lien=\"(.*?)\" nom=\"(.*?)\">([\s\S]*?)<\/citation>/g, '<br /><span class="citation"><a href="$1">Citation : $2</a></span><div class="citation2">$3</div>');
		field = field.replace(/<citation>([\s\S]*?)<\/citation>/g, '<br /><span class="citation">Citation</span><div class="citation2">$1</div>');
		field = field.replace(/<taille valeur=\"(.*?)\">([\s\S]*?)<\/taille>/g, '<span class="$1">$2</span>');
		
		for (var i=0, c=smiliesName.length; i<c; i++) {
			field = field.replace(new RegExp(" " + smiliesName[i] + " ", "g"), "&nbsp;<img src=\"" + smiliesPath + smiliesUrl[i] + "\" alt=\"" + smiliesUrl[i] + "\" />&nbsp;");
		}
		
		document.getElementById(previewDiv).innerHTML = field;
	}
		var content = encodeURIComponent(document.getElementById(<gras>textareaId).value);