從對象數組中提取 object 元素並將它們組織成數組

Question

經過幾天的拉扯，我決定尋求幫助：

• 我有一組對象，每個雜貨店商品一個。 每個 object 都有 3 個屬性：category（商品類別的字符串）、itemName（商品本身的字符串）和 onSale（布爾值是否在銷售）：

   var itemData = [ { category: 'fruit', itemName: 'apple', onSale: false }, { category: 'canned', itemName: 'beans', onSale: false }, { category: 'canned', itemName: 'corn', onSale: true }, { category: 'frozen', itemName: 'pizza', onSale: false }, { category: 'fruit', itemName: 'melon', onSale: true }, { category: 'canned', itemName: 'soup', onSale: false }, ];

• 我需要將其轉換為 object，其屬性為 object 類別。 每個屬性都是一個數組，其中包含與屬性對應的 itemName 中的值：

   { fruit: ['apple', 'melon($)'], canned: ['beans', 'corn($)', 'soup'], frozen: ['pizza'] };

• 當我嘗試這樣做時，我最終得到方向正確的值，除了它們被重復：

   { fruit: [ 'apple', 'apple', 'melon', 'melon', 'melon' ], canned: [ 'beans', 'beans', 'corn', 'corn', 'corn', 'soup', 'soup', 'soup' ], frozen: [ 'pizza', 'pizza' ] }

• 我花了幾個小時試圖找出我哪里出錯了，但無濟於事。 這是我的代碼：

   function organizeItems (array){ //create output obj var output = {} //iterate over the array for(var i = 0; i < array.length; i++){ //iterate over the object in the array for(var category in array[i]){ //if value of category isn't in output add the value to output as an empty array if(output[array[i]["category"]] === undefined){ output[array[i]["category"]] = []; //if not --> push the itemName to the category } else{ output[array[i]["category"]].push(array[i]["itemName"]) } } } return output }

如何避免重復並最終在 arrays 中獲得正確的值？

Answer 1

for(var category in array[i]){...

您不必遍歷每個 object 的條目，因為這會將不必要的元素添加到數組中，例如 output 'melon', 'melon', 'melon'

---

您可以使用Array.prototype.reduce ：

 const itemData = [ { category: 'fruit', itemName: 'apple', onSale: false }, { category: 'canned', itemName: 'beans', onSale: false }, { category: 'canned', itemName: 'corn', onSale: true }, { category: 'frozen', itemName: 'pizza', onSale: false }, { category: 'fruit', itemName: 'melon', onSale: true }, { category: 'canned', itemName: 'soup', onSale: false }, ]; const object = itemData.reduce((acc,el) => (acc[el.category]??= [], acc[el.category].push(el.itemName + (el.onSale? '($)': '')), acc), {}) console.log(object)

Answer 2

您可以按category分組並調整itemName 。

 const itemData = [{ category: 'fruit', itemName: 'apple', onSale: false }, { category: 'canned', itemName: 'beans', onSale: false }, { category: 'canned', itemName: 'corn', onSale: true }, { category: 'frozen', itemName: 'pizza', onSale: false }, { category: 'fruit', itemName: 'melon', onSale: true }, { category: 'canned', itemName: 'soup', onSale: false }], result = itemData.reduce((r, { category, itemName, onSale }) => { itemName += onSale? ' ($)': ''; (r[category]??= []).push(itemName); return r; }, {}); console.log(result);

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Answer 3

 var itemData = [ { category: 'fruit', itemName: 'apple', onSale: false }, { category: 'canned', itemName: 'beans', onSale: false }, { category: 'canned', itemName: 'corn', onSale: true }, { category: 'frozen', itemName: 'pizza', onSale: false }, { category: 'fruit', itemName: 'melon', onSale: true }, { category: 'canned', itemName: 'soup', onSale: false }, ]; // // expected result... // { // fruit: ['apple', 'melon($)'], // canned: ['beans', 'corn($)', 'soup'], // frozen: ['pizza'] // }; console.log( itemData.reduce((result, item) => { // destructure `itemData`'s array `item`. const { category, itemName, onSale } = item; // (create and/or) access the `category` specific array. const categoryArray = (result[category]??= []); // push the correct (depending on `onSale` state) form of a category item. categoryArray.push(`${ itemName }${ (onSale === true)? '($)': '' }`); return result; }, {}) );

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