javascriptはIE 6,7,8でtrim()をサポートしていません.

String.prototype.trim = function() {
    return this.replace(/^\s+|\s+$/g,"");
}
String.prototype.ltrim = function() {
    return this.replace(/^\s+/,"");
}
String.prototype.rtrim = function() {
    return this.replace(/\s+$/,"");
}

function trim(stringToTrim) {
    return stringToTrim.replace(/^\s+|\s+$/g,"");
}
function ltrim(stringToTrim) {
    return stringToTrim.replace(/^\s+/,"");
}
function rtrim(stringToTrim) {
    return stringToTrim.replace(/\s+$/,"");
}