Get value by key

@param {KeyItem} key
@returns {String|Object}
function(key) {
        var value;
        if (key.indexOf('.') == -1) {
            value = this.configObj[key];
        } else {
            var keyArray = key.split('.');
            var keyStr = keyArray[0];
            value = this.configObj[keyStr];
            for(var i= 1,len=keyArray.length;i<len;i++) {
                if (!value && i < len-1) {
                    exitProcess('the var ['+keyStr + '] is empty.', this.alarm);
                    return undefined;
                }
                var keyNow = keyArray[i];
                keyStr += '.'+keyNow;
                value = value[keyNow];
            }
        }
        slogger.debug('load var ['+key+'],value:',value);
        return value;
    }