前端公共方法封装:

/**
 * 判断字符串是否为空或null
 * @param object
 * @returns {*}
 */
var isNullorEmpty = function (object) {
    return isNull(object);
}

/**
 * 是否为空
 * @param object
 * @returns {Boolean}
 */
function isNull(object) {
	var isNull = false;
	if (object == undefined || object == null || object == "" || object == "null") {
	  isNull = true;
	}
	return isNull;
}

方法调用:

    var aa = '';
    if (isNullorEmpty(aa)) {
       console.log("内容为空")
    }else{
       console.log("内容不为空")
    }