September 2022
Intermediate to advanced
585 pages
8h 17m
Chinese
Content preview from JavaScript 经典实例：第三版
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128
｜
第
5
章
如果需要编写更复杂的条件，
find()
和
findIndex()
方法的强大就体现出来了。请看
下述代码，这段代码查找落在指定年份中的第一个日期。
//
记住，
Date
构造函数接受的月份值从
0
开始计数
//
因此，
10
表示第
11
个月，即十一月
const
dates = [
new
Date(2021, 10, 20),
new
Date(2020, 3, 12),
new
Date(2020, 5, 23),
new
Date(2022, 3, 18)];
//
查找落在
2020
年中的第一个日期
const matchingDate = dates.find(date => date.getFullYear() === 2020);
console.log(matchingDate); // 'Sun Apr 12 2020 ...'
使用
indexOf()
就达不到这种效果，因为我们要检查数组元素的一个属性（其实，
indexOf()
方法甚至无法比较两个
Date
对象是否相等，因为该方法只能检查对象引
用是否一致）。
5.14.4
参考
如果你想编写一个函数查找多个结果，可能需要使用
5.9
节介绍的
filter()
函
数。
箭头句法的进一步说明见
6.2
节。
5.15
删除或替换数组元素
5.15.1
问题
你想查找指定的值在数组中出现的位置，把对应的元素删除或替换掉。
5.15.2
方案
首先，使用
indexOf()
方
法找到想删除的元素所在的位置。然后，在下面两种方式
中选择一个。
对小型数组来说，最简洁的方案是使用不想要的元素两侧的元素重新构建一个数组。 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.