javascript - 函数(导出)返回错误 "Cannot set property ' weekDay' 未定义”

Question

所以我正在阅读 Eloquent JS 书中的“模块”章节，并且遇到了函数(导出)部分的问题。

(function (exports) {
var names = ["Sunday", "Monday", "Tuesday", "Wednesday",
           "Thursday", "Friday", "Saturday"];

exports.name = function (number) {
    return names[number];
};
exports.number = function (name) {
    return names.indexOf(name);
};
})(this.weekDay = {});

console.log(weekDay.name(1));

返回

Cannot set property "weekDay" of undefined

但是，在本书网站上的在线编辑器中，完全相同的代码运行没有问题并返回“Monday”。

我想知道这是否是 Adob​​e Brackets 的问题。

Answer 1

使用不依赖于在全局脚本作用域中执行的模块模式，其中 this 是全局对象。我推荐

var weekDay = (function (exports) {
    var names = ["Sunday", "Monday", "Tuesday", "Wednesday",
               "Thursday", "Friday", "Saturday"];
    return {
        name: function (number) {
            return names[number];
        },
        number: function (name) {
            return names.indexOf(name);
        }
    };
}());

所以，是的，这是由您的环境引起的，但代码首先很脆弱。如果您想继续使用 exports 功能，您也可以这样做

var weekDay;
(function (exports) {
    …
})(weekDay = {});

或者检查 How to get the global object in JavaScript?和 Getting a reference to the global object in an unknown environment in strict mode .