用JavaScript函數參數訪問對象

Question

我想在JS中製作一種「購物清單」。我無法通過函數的參數訪問對象。

shopList = { 
 
    create: function createList(listName) { 
 
    listName = {}; 
 
    listName["Banana"] = 2 
 
    }, 
 

 
    output: function output(listName) { 
 
    console.log(listName) 
 
    }, 
 

 
}; 
 

 
shopList.create('list') 
 
shopList.output('list')

當我運行shopList.output '名單' 返回。如何通過參數訪問對象？希望這不是重複的，現在幾個小時一直在Google上搜索，並沒有取得任何進展。

Answer 1

如果您希望能夠使用動態名稱配置列表，則需要使用bracket notation在this對象內創建列表。就像這樣：

var shopList = { 
 
    create: function createList(listName) { 
 
     this[listName] = {}; 
 
     this[listName]["Banana"] = 2 
 
    }, 
 

 
    output: function output(listName) { 
 
     return this[listName]; 
 
    } 
 
}; 
 

 
shopList.create('list'); 
 
console.log(shopList.output('list'));

然而，正如在評論中指出的@armchairdj，最好創建一個容器專用屬性來保存列表：如果你想避免

var shopList = { 
    lists: {}, 

    create: function createList(listName) { 
     this.lists[listName] = {}; 
     this.lists[listName]["Banana"] = 2 
    }, 

    output: function output(listName) { 
     return this.lists[listName]; 
    } 
}; 

Answer 2

通過天真​​地添加任意的用戶提供的鍵來打破showList對象的方法，你應該爲你的列表創建一個內部命名空間。

var shopList = { 
 
    lists: {}, 
 

 
    create: function (listName) { 
 
    this.lists[listName] = this.lists[listName] || {}; 
 

 
    this.lists[listName].Banana = 2; 
 
    }, 
 

 
    output: function (listName) { 
 
    var list = this.lists[listName]; 
 

 
    if (!list) { 
 
     return console.log('No list named ' + listName + ' found.'); 
 
    } 
 

 
    console.log(list) 
 
    } 
 
}; 
 

 
shopList.create('output'); 
 
shopList.output('output'); 
 
shopList.create('foo'); 
 
shopList.output('foo'); 
 
shopList.output('bar');