ajax vs请求openWeatherMap

Question

so i need to draw a icons on map when status is ok. But when I change request to ajax i got

Unexpected token u in JSON at position 0

when i go back to request everything work fine... but I need to have exceptions handling, so thats why Ajax

JS

    function displayXML()
{
    if (this.readyState == 4)
    { 
        proccessResults();

        if (this.status == 200)
        {
            console.log(this.responseXML);

        } else {
            console.log(this.status);
            alert('Something went wrong')
        }
    }
}
var getWeather = function(northLat, eastLng, southLat, westLng) {
    gettingData = true;
    var requestString = "http://api.openweathermap.org/data/2.5/box/city?bbox="
        + westLng + "," + northLat + ","
        + eastLng + "," + southLat + ","
        + map.getZoom()
        + "&cluster=yes&format=json"
        + "&APPID=" + openWeatherMapKey;
    var ajax = new XMLHttpRequest();
    ajax.open('GET', requestString, true);
    ajax.onreadystatechange = displayXML;
    ajax.send();
    // request = new XMLHttpRequest();
    // request.onload = proccessResults;
    // request.open("get", requestString, true);
    // request.send();
};

var proccessResults = function() {

    var results = JSON.parse(this.responseText);
    if (results.list.length > 0) {
        resetData();
        for (var i = 0; i < results.list.length; i++) {
            geoJSON.features.push(jsonToGeoJson(results.list[i]));
        }
        drawIcons(geoJSON);
    }
};

respone:

{"cod":"200","calctime":0.0007,"cnt":2,"list":[{"id":3082473,"name":"Wejherowo","coord":{"lon":18.23559,"lat":54.605679},"main":{"temp":15.33,"pressure":1012,"humidity":93,"temp_min":15,"temp_max":15.56},"dt":1468456804,"wind":{"speed":0.5,"deg":0},"clouds":{"all":20},"weather":[{"id":801,"main":"Clouds","description":"few clouds","icon":"02n"}]},{"id":3099424,"name":"Gdynia","coord":{"lon":18.531879,"lat":54.51889},"main":{"temp":15.3,"pressure":1012,"humidity":93,"temp_min":15,"temp_max":15.56},"dt":1468456816,"wind":{"speed":0.5,"deg":0},"clouds":{"all":20},"weather":[{"id":801,"main":"Clouds","description":"few clouds","icon":"02n"}]}]}

Answer 1

Your proccessResults function is not being called with any parameters. It has no idea what this (or this.responseText ) is. You are trying to parse the string "undefined" as JSON. That's where your "Unexpected token u" error comes from.

Try to change your processResults function to take a parameter :

var proccessResults = function(jsonString) {    
    var results = JSON.parse(jsonString);
    if (results.list.length > 0) {
        resetData();
        for (var i = 0; i < results.list.length; i++) {
            geoJSON.features.push(jsonToGeoJson(results.list[i]));
        }
        drawIcons(geoJSON);
    }
}

Then when you call it, pass it the this.responseText :

function displayXML(){
    if (this.readyState == 4){ 
        proccessResults(this.responseText);

        if (this.status == 200){
            console.log(this.responseXML);

        }
        else {
            console.log(this.status);
            alert('Something went wrong')
        }
    }
}