js去除字符串首尾字符

String.prototype.trim = function (char, type) {
    if (char) {
        if (type == 'left') {
            return this.replace(new RegExp('^\\'+char+'+', 'g'), '');
        } else if (type == 'right') {
            return this.replace(new RegExp('\\'+char+'+$', 'g'), '');
        }
        return this.replace(new RegExp('^\\'+char+'+|\\'+char+'+$', 'g'), '');
    }
    return this.replace(/^\s+|\s+$/g, '');
};