JS-将键从对象移动到另一个对象

debugcn 发表于 Dev

马哈利克

我有书籍清单：

let myBooks = [{"id":8,"name":"Don Quijote","author":"Cervantes"},{"id":9,"name":"Romeo and Juliet","author":"Shakespeare"},{"id":10,"name":"Hamlet","author":"Shakespeare"},{"id":11,"name":"Othello","author":"Shakespeare"},{"id":"12","nazev":"Antigona","autor":"Sofokles"}]

我需要找出如何与作者一起创建新对象，以及他们要进行多少次myBooks这样的工作：

let authorsInMyBooks = [{"Cervantes":1},{"Shakespeare":3},{"Sofokles":1}]

我尝试了这个：

for (i = 0; i < myBooks.length; i++) {
            if (myBooks[i].author in authorsInMyBooks) {
                authorsInMyBooks[myBooks[i].author] += 1;
            } else {
                authorsInMyBooks[myBooks[i].author] = 1;
            }
        }

但是输出是：

[{"Cervantes":5, "Shakespeare":9, "Sofokles":1}]

当我向其中添加新书时，每次都使用for循环调用function myBooks

马埃里·阿里（Maheer Ali）

您需要使用一个空对象作为的初始值，authorsInMyBooks然后用于map()获取数组。

let myBooks = [{"id":8,"name":"Don Quijote","author":"Cervantes"},{"id":9,"name":"Romeo and Juliet","author":"Shakespeare"},{"id":10,"name":"Hamlet","author":"Shakespeare"},{"id":11,"name":"Othello","author":"Shakespeare"},{"id":"12","nazev":"Antigona","autor":"Sofokles"}]

let authorsInMyBooks = {}
for (let i = 0; i < myBooks.length; i++) {
   if (authorsInMyBooks[myBooks[i].author]) {
      authorsInMyBooks[myBooks[i].author] += 1;
   } else {
      authorsInMyBooks[myBooks[i].author] = 1;
   }
}

authorsInMyBooks = Object.entries(authorsInMyBooks).map(([k, v]) => ({[k]: v}));

console.log(authorsInMyBooks)

您可以使用 reduce()

let myBooks = [{"id":8,"name":"Don Quijote","author":"Cervantes"},{"id":9,"name":"Romeo and Juliet","author":"Shakespeare"},{"id":10,"name":"Hamlet","author":"Shakespeare"},{"id":11,"name":"Othello","author":"Shakespeare"},{"id":"12","nazev":"Antigona","autor":"Sofokles"}]

const res = myBooks.reduce((ac, {author}) => {
  ac[author] = (ac[author] || 0) + 1
  return ac;
}, {})

const authorsInMyBooks = Object.entries(res).map(([k, v]) => ({[k]: v}));

console.log(authorsInMyBooks)

本文收集自互联网，转载请注明来源。

如有侵权，请联系[email protected] 删除。