比较两个数组以获得一个数组的下一个值

Question

我正在尝试获取另一个数组的下一个值。

import matplotlib
import matplotlib.pyplot as plt
from matplotlib.colors import ListedColormap
from matplotlib.collections import PatchCollection
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(111)
patches_list = []
color_list = []
patches_list.append(matplotlib.patches.Rectangle((-200,-100), 400, 200))
color_list.append('yellow')
patches_list.append(matplotlib.patches.Rectangle((0,150), 300, 20))
color_list.append('red')
patches_list.append(matplotlib.patches.Rectangle((-300,-50), 40, 200))
color_list.append('#0099FF')
patches_list.append(matplotlib.patches.Circle((-200,-250), radius=90))
color_list.append('#EB70AA')

our_cmap = ListedColormap(color_list)
patches_collection = PatchCollection(patches_list, cmap=our_cmap)
patches_collection.set_array(np.arange(len(patches_list)))
ax.add_collection(patches_collection)

plt.xlim([-400, 400])
plt.ylim([-400, 400])
plt.show()

因此，当我搜索var books = ["book1", "book3"]; var bookprice = [["book1", "$5"], ["book2", "$2"], ["book3", "$7"]]; var list = []; for (key in bookprice) { if(bookprice.hasOwnProperty(key)){ list.push(bookprice[key][0]); } } list = ["book1", "book2", "book3"]; 时，它将返回book1。 我坚持下一步需要做的事情。我需要$5来获取每个索引的索引吗？

Answer 1

现在，当您获得列表时，可以使用Array.find()查找具有该书名的内部数组，然后使用[1]上的find()获取第二个元素，即价格结果。

使用Array.find()

var bookprice = [
  ["book1", "$5"],
  ["book2", "$2"],
  ["book3", "$7"]
];

var list = ["book1", "book2", "book3"];
var bookName = list[0];
var price = bookprice.find(innerArray => innerArray[0] === bookName)[1];
console.log(price);

FOR IE（纯JS）

var bookprice = [
  ["book1", "$5"],
  ["book2", "$2"],
  ["book3", "$7"]
];

var list = ["book1", "book2", "book3"];
var bookName = list[0];
var price;
for(var i=0; i<bookprice.length; i++){
  if(bookprice[i][0] === bookName){
    price = bookprice[i][1];
    break;
  }
}
console.log(price);

Answer 2

使用Array.find和destructuration

const bookprice = [
  ['book1', '$5'],
  ['book2', '$2'],
  ['book3', '$7'],
];

const list = ['book1', 'book2', 'book3'];

const bookName = list[0];

const [
  ,
  price,
] = bookprice.find(([
  name,
  price,
]) => name === bookName);

console.log(price);

---

正如有人已经在评论中告诉您的那样，最好是创建一个对象而不是一个数组数组。

const bookprice = {
  book1: '$5',
  book2: '$2',
  book3: '$7',
};

const list = ['book1', 'book2', 'book3'];

const bookName = list[0];

const price = bookprice[bookName];

console.log(price);

---

兼容的IE 11

var bookprice = [
  ['book1', '$5'],
  ['book2', '$2'],
  ['book3', '$7'],
];

var list = ['book1', 'book2', 'book3'];

var bookName = list[0];

var price;

for (var i = 0; i < bookprice.length && price === void 0; i += 1) {
  if (bookprice[i][0] === bookName) {
     price = bookprice[i][1];
  }
}

console.log(price);

Answer 3

var bookprice = [["book1", "$5"], ["book2", "$2"], ["book3", "$7"]];

var list = ["book1", "book2", "book3"];
var bookName = list[0];
var price = bookprice[list.indexOf(bookName)][1];
console.log(price);

Answer 4

如果bookprice是对象，那么检索特定书籍的价格将很容易。 bookprice应该是：

var bookprice = {
    "book1": "$5", 
    "book2": "$2",
    "book3": "$7"
};

然后取回一本书的价格将非常简单：

var book = "book1";
var price = bookprice[book];

将bookprice转换为对象：

使用for循环（对于旧的浏览器）：

var bookpriceObject = {};
for(var i = 0; i < bookprice.length; i++) {
    bookpriceObject[bookprice[i][0]] = bookprice[i][1];
}

使用reduce：

var bookpriceObject = bookprice.reduce(function(acc, book) {
    acc[book[0]] = book[1];
    return acc;
}, {});

可以使用箭头功能将其缩短：

var bookpriceObject = bookprice.reduce((acc, book) => (acc[book[0]] = book[1], acc), {});

Answer 5

将Array.find用作https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find

var bookprice = [
  ["book1", "$5"],
  ["book2", "$2"],
  ["book3", "$7"]
];

function getBookPrice(bookname) {
    let book = bookprice.find(item => item[0] === bookname)
    if (book) {
        return book[1];
    } else {
        console.log('No book Found');
        return 0;
    }
}

console.log(getBookPrice('book1'));
console.log(getBookPrice('book2'));
console.log(getBookPrice('book3'));
console.log(getBookPrice('randombook'));