如何使用异步功能访问天气 API 降雨数据

Question

我正在使用 OpenWeatherMap API 来计算前 5 天的降水量总和。我在访问湿度或温度等值时没有问题，但我在汇总前 5 天的所有降雨值时遇到了问题。雨仅在实际测量的对象响应中可用。以下是测量下雨时的示例：

您可以看到每小时下雨。18.rain['1h']。 我的问题在于将它们全部汇总。

这是我的完整代码：

//converts current unix date from miliseconds to seconds and subtracts seconds from variable daysAgo
function getDaysAgo(days) {
    return Math.floor((Date.now() / 1000) - (86400 * days)) //returns date of privious 5 days from now.
}
//fetchs historic hourly weather data for rain.
async function getDataForDaysAgo(days) {
    let daysAgo = getDaysAgo(days) //nest getDaysAgo function to variable
    const apiURL = `http://api.openweathermap.org/data/2.5/onecall/timemachine?lat=29.8833&lon=-97.9414&dt=${daysAgo}&appid=` //calls historic weather api using privious days
    const apiResponse = await fetch(apiURL)  //fetch data
    const responseJson = await apiResponse.json() //converts data to json
    var total = 0
    console.log(responseJson);

    responseJson.hourly.forEach(hour => { //loops through each 1hr record of 24
          //if no rain is recorded, rain data is not available. system reprots: NaN
          if (isNaN(hour.rain['1h'])){
            hour.rain['1h'] = 0   //if rain is NaN, change that value to 0.
          }//else(total += hour.rain);
          else{
            total += hour.rain['1h']
          }//otherwise sum all available rain values.
          //total += hour.rain

    });
    console.log(`getDataForDaysAgo(${days}) returns ${total}`) //logs total rain values for each 24hr period
    return total
}
//call above fetch function with appropriate historic 'daysAgo'
async function getDataSums() {
    var data1 = await getDataForDaysAgo(5)
    var data2 = await getDataForDaysAgo(4)
    var data3 = await getDataForDaysAgo(3)
    var data4 = await getDataForDaysAgo(2)
    var data5 = await getDataForDaysAgo(1)
    return data1 + data2 + data3 + data4 + data5; //returns sum of 5 day rain values
}

getDataSums().then(result => { //waits for getDataSums and return result
    var totalRainInches = parseFloat((result)*25.4); //converts to mm to inches
      document.getElementById('precip5day').innerHTML = "Five Day Precipication Accumulation:"
      document.getElementById('precipValue').innerHTML = totalRainInches.toFixed(2) + "″"
    //proof of concept conditional statment that gives recommendations for trail use
    //based on 5 day rain totals and writes to index.html file
    if (totalRainInches <= 0.50){
      document.getElementById('conditions').innerHTML = "Hiking and mountain biking should be okay"
    } else if (totalRainInches < 3 ){
      document.getElementById('conditions').innerHTML = "Due to recent rain activity, use best judgement when hiking or mountain biking"
    } else if (totalRainInches > 7 ){
      document.getElementById('conditions').innerHTML = "Due to heavy rainfall, trails should not be used"
    }else {
      document.getElementById('conditions').innerHTML = "Something broke :("
    }
});

我很幸运将所有湿度值加起来：

    responseJson.hourly.forEach(hour => {
         
          if (isNaN(hour.humidity)){
            hour.humidity = 0   
          }
          else{
            total += hour.humidity
          }

但是当谈到雨值时，我空手而归，并收到错误消息，即雨变量未定义。任何想法？谢谢！ 另外，这里有一个指向 previous question 的链接，它让我走到了这一步。

Answer 1

您确定rain 出现在从 0 到 23 的所有时间吗？如果它丢失了，你会得到"Uncaught TypeError: Cannot read property '1h' of undefined"，就像我下面的示例一样。如果你检查它，它应该总结得很好。

// prep 24 hours with rain and humidity
var hourly = []
for (let i = 0; i < 24; i++) {
  hourly[i] = {
    rain: {
      '1h': 0.5
    },
    humidity: 2.2
  }
}

// your code in a function
function sumRain(hourly) {
  var total = 0;
  hourly.forEach(hour => {
    // uncomment the next line to check for 'rain' being present
    // if (hour.rain)
    if (isNaN(hour.rain['1h'])) {
      hour.rain['1h'] = 0
    } else {
      total += hour.rain['1h']
    }
  });

  return total;
}

console.log(sumRain(hourly))

// modify hourly so rain is missing from one of the hours
delete hourly[11].rain;

// now sumrain throws an exception unless you check for hour.rain being present before trying to sum it up
console.log(sumRain(hourly))