June 2021
Intermediate to advanced
290 pages
9h 21m
Chinese
Content preview from Node与Express开发（第2版）
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230
｜
第
19
章
存需要一段时间，并且是异步完成的。如果在第一次缓存刷新完成前进来了多个请求，要
是没有这个属性，这些请求就又会开始缓存刷新的工作。确实，这样也不会有什么害处，
但它会发出更多
API
调
用，而这些调用是不必要的。这个布尔变量就是一个标志，就好像
在对所有后续请求说：“我们正在忙这事儿呢。”
第
7
章创建了一个
getWeatherData
函数，当时使用的是模拟数据，这里把它整个替换掉。
需要做的是打开
lib/middleware/weather
.js
，替换
getWeatherData
函数：
const weatherData = require('../weather')
const getWeatherData = weatherData([
{
name: 'Portland',
coordinates: { lat: 45.5154586, lng: -122.6793461 },
},
{
name: 'Bend',
coordinates: { lat: 44.0581728, lng: -121.3153096 },
},
{
name: 'Manzanita',
coordinates: { lat: 45.7184398, lng: -123.9351354 },
},
])
现在，我们的天气组件就有实时数据了。
19.4
小结
对于第三方
API
集成能够做到什么，实际上我们只是触及了其皮毛。环顾四周，不断有新
的
API
冒出来
，提供着你所能想象的各种类型的数据 ...
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