我写了一些 javascript 从 url 获取天气信息。但谷歌浏览器显示错误:
Uncaught TypeError: Cannot call method 'addEventListener' of null weather.html:37
(anonymous function)
有什么建议可以解决这个问题吗?谢谢!
<html>
<head>
<title>My weather</title>
<script type="text/javascript">
function fetchWeather(){
var xmlHttp = new XMLHttpRequest(); // Initialize our XMLHttpRequest instance
xmlHttp.open("GET", "http://classes.engineering.wustl.edu/cse330/content/weather_json.php", true);
xmlHttp.addEventListener("load", ajaxCallback, false);
xmlHttp.send(null);
}
function ajaxCallback(event){
var htmlParent = document.getElementById("weatherWidget"); // Get the HTML element
var jsonData = JSON.parse(event.target.responseText);
var loc = document.getElementById("weatherWidget").getElementsByClassName("weather-loc")[0];
loc.appendChild(document.createTextNode(jsonData.location.city+" "+jsonData.location.state));
var humidity = document.getElementById("weatherWidget").getElementsByClassName("weather-humidity")[0];
humidity.appendChild(document.createTextNode("Humidity: "+jsonData.atmosphere.humidity+"%"));
var temp = document.getElementById("weatherWidget").getElementsByClassName("weather-temp")[0];
temp.appendChild(document.createTextNode("Currently: "+jsonData.current.temp));
var tomorrow = document.getElementById("weatherWidget").getElementsByClassName("weather-tomorrow")[0];
tomorrow.appendChild(document.setAttribute("src", jsonData.current.temp));
tomorrow.alt = jsonData.tomorrow.text;
tomorrow.src = "http://us.yimg.com/i/us/nws/weather/gr/"+jsonData.tomorrow.code+"ds.png"
var dayaftertomorrow = document.getElementById("weatherWidget").getElementsByClassName("weather-dayaftertomorrow")[0];
dayaftertomorrow.appendChild(document.setAttribute("src", jsonData.current.temp));
dayaftertomorrow.alt = jsonData.dayafter.text;
dayaftertomorrow.src = "http://us.yimg.com/i/us/nws/weather/gr/"+jsonData.dayafter.code+"ds.png"
}
document.getElementById("update").addEventListener("click", fetchWeather, false); // bind fetchWeather() to the DOMContentLoaded event
//so that your weather widget is automatically initialized
//when the page is loaded
</script>
</head>
<body>
<div class="weather" id="weatherWidget">
<div class="weather-loc"></div>
<div class="weather-humidity"></div>
<div class="weather-temp"></div>
<img class="weather-tomorrow" />
<img class="weather-dayaftertomorrow" />
</div>
<button id="update">Update</button>
</body>
</html>