Javascript 如何从for语句中的异步回调中获得结果
我想显示ajax post mysql查询的结果，并通过结果进一步细化到getDistanceMatrix，这是一个异步函数，作为回调的一部分返回距离值 我读过几篇关于异步函数（如等）的文章，选择使用回调作为最简单的理解方法，但无法使其工作，因此遇到了麻烦 我正在使用javascript和一些php，如果我不运行getDistanceMatrix，它就可以显示结果，但无法计算出如何从函数中获取kms值以供if语句使用，从而进一步优化要显示的结果。 我也尝试过在回调函数callbacku calcDistancekms中包含if语句和表html，但是没有显示任何内容。 我认为问题在于代码在getDistanceMatrix完成之前就已经完成了，但是不知道如何及时从这个函数中获得运行html表的结果。 我已经包括了下面的javascript部分 ` $document.readyfunction{Javascript 如何从for语句中的异步回调中获得结果,javascript,asynchronous,Javascript,Asynchronous,我想显示ajax post mysql查询的结果，并通过结果进一步细化到getDistanceMatrix，这是一个异步函数，作为回调的一部分返回距离值 我读过几篇关于异步函数（如等）的文章，选择使用回调作为最简单的理解方法，但无法使其工作，因此遇到了麻烦 我正在使用javascript和一些php，如果我不运行getDistanceMatrix，它就可以显示结果，但无法计算出如何从函数中获取kms值以供if语句使用，从而进一步优化要显示的结果。 我也尝试过在回调函数callbacku calc
$("#findride").submit(function(){
//js variables from form
$.ajax({
url: 'includes/findride.inc.php',
type: 'POST',
dataType:"json",
data: { rdate:rdate, rtime:rtime, },
success: function(data) {
//isEmpty function
if(isEmpty(data)) {
$("#result").html("<p class='loginError' >No Rides match your Search</p>");
}
else
{
var output =
"<table><thead><tr><th class='tablehdr-15'>Ride ID</th><th class='tablehdr-60'>Destination</th><th class='tablehdr-25'>Arrival Time</th></thead><tbody>";
for (var i in data) {
var driver_lng = data[i].user_lng;
// other variables from mysql
var origin = new google.maps.LatLng(-36.78961120, 174.75189440);
var destination = new google.maps.LatLng(-36.80272570, 174.74423420);
var distanceResult1;
function calcDistance (fromLat, fromLng, toLat, toLng) {
return google.maps.geometry.spherical.computeDistanceBetween(
new google.maps.LatLng(fromLat, fromLng), new google.maps.LatLng(toLat, toLng));
}
var calcD = calcDistance(latdb, lngdb, lats, lngs);
calculateDistanceDriver(origin, destination, Callback_calcDistance);
function calculateDistanceDriver(origin, destination, ref_Callback_calcDistance) {
var service = new google.maps.DistanceMatrixService();
var kms;
service.getDistanceMatrix(
{
origins: [origin],
destinations: [destination],
travelMode: google.maps.TravelMode.DRIVING,
unitSystem: google.maps.UnitSystem.METRIC
}, function (response, status) {
if (status != google.maps.DistanceMatrixStatus.OK) {
$('#result1').html(err);
}
else
{
var origin = response.originAddresses[0];
var destination = response.destinationAddresses[0];
if (response.rows[0].elements[0].status === "ZERO_RESULTS") {
$('#result1').html("No result for this search");
}
else
{
var distance = response.rows[0].elements[0].distance;
var distance_value = distance.value;
var distance_text = distance.text;
var kms = distance_text.substring(0, distance_text.length - 3);
//How can I make kms available for the if ((calcD < 2000) .. statement below?
$('#result1').html("Result = " + kms);
console.log("distance result a " + kms);
if(typeof ref_Callback_calcDistance === 'function'){
ref_Callback_calcDistance(kms)
}
}
}
});
}
function Callback_calcDistance(kms) {
console.log("distanceResult " + kms);
distanceResult1 = kms;
}
console.log("distanceResult1 " + distanceResult1);
//I want to use kms here for following if statement
// if ((calcD < 2000) && (seatsreq <= freeseats) && (distanceResult1 <= extra_dist)) {
if ((calcD < 2000) && (seatsreq <= freeseats)) {
output +=
"<tr><td class='tablehdr-15'>" +
data[i].ride_id +
"</td><td class='tablehdr-60'><a href='includes/ridedetails.inc.php?rideid=" + data[i].ride_id + "' target='_blank'>" +
data[i].dest_address +
"</a></td><td class='tablehdr-25'>" +
data[i].ride_time +
"</td></tr>";
}
}
output += "</tbody></table>";
$("#result").html(output);
$("table").addClass("table-300");
}
},
error: function(e) {
console.log(e.message);
}
});
event.preventDefault();
});
我希望能够使用getDistanceMatrix调用的结果进一步细化ajax帖子中的结果。在全局中声明var kms，然后您将获得kms值
Callback\u calcDistance函数未调用，因此请检查。以下是解决方案。我在回调中移动了if语句，并创建了第二个输出变量作为新表
<main>
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js"></script>
<script src="https://maps.googleapis.com/maps/api/js?key=API_KEY&libraries=places,geometry&callback=initAutocomplete"
async defer></script>
<script>
$(document).ready(function(){
$("#findride").submit(function(){
var rdate = $("#rdate").val();
var rtime = $("#rtime").val();
console.log(rtime);
console.log(rdate);
var lats = $("#lat").val();
var lngs = $("#lng").val();
var seatsreq = $("#seatsreq").val();
var kms;
$.ajax({
url: 'includes/findride1.inc.php',
type: 'POST',
dataType:"json",
data: { rdate:rdate, rtime:rtime, seatsreq:seatsreq },
success: function(data) {
console.log(data);
function isEmpty(obj) {
for(var key in obj) {
if(obj.hasOwnProperty(key))
return false;
}
return true;
}
if(isEmpty(data)) {
$("#result").html("<p class='loginError' >No Rides match your Search</p>");
}
else
{
var output =
"<table><thead><tr><th class='tablehdr-15'>Ride ID</th><th class='tablehdr-60'>Destination</th><th class='tablehdr-25'>Arrival Time</th></thead><tbody></tbody></table>";
$("#result").html(output);
$("table").addClass("table-300");
//$("#result").hide();
var output1 = "<table><tbody>";
for (let i in data) {
var latdb = data[i].lat;
var lngdb = data[i].lng;
var extra_dist = data[i].extra_dist;
var freeseats = data[i].free_seats;
var driver_lat = data[i].user_lat;
var driver_lng = data[i].user_lng;
var driver_dist = data[i].driver_dist;
var origin = new google.maps.LatLng(-36.78961120, 174.75189440);
var destination = new google.maps.LatLng(-36.80272570, 174.74423420);
var origin1 = "-36.78961120, 174.75189440";
var destination1 = "-36.80272570, 174.74423420";
var distanceResult1;
var directionsService = new google.maps.DirectionsService();
var service = new google.maps.DistanceMatrixService();
var calcD = calcDistance(latdb, lngdb, lats, lngs);
function calcDistance (fromLat, fromLng, toLat, toLng) {
return google.maps.geometry.spherical.computeDistanceBetween(
new google.maps.LatLng(fromLat, fromLng), new google.maps.LatLng(toLat, toLng));
}
calcRoute();
function calcRoute() {
var waypts = [
{
location: "-36.7612802,174.7516339",
stopover: true
}
];
var request = {
origin: origin1,
destination: destination1,
waypoints: waypts,
optimizeWaypoints: false,
travelMode: google.maps.TravelMode.DRIVING,
unitSystem: google.maps.UnitSystem.METRIC
};
directionsService.route(request, function(response, status) {
if (status == google.maps.DirectionsStatus.OK) {
var total_distance = 0.0;
for (var i=0; i<response.routes[0].legs.length; i++) {
total_distance += response.routes[0].legs[i].distance.value;
}
console.log("distance value " + total_distance);
}
});
}
calculateDistanceDriver(origin, destination, Callback_calcDistance);
function calculateDistanceDriver(origin, destination, ref_Callback_calcDistance) {
service.getDistanceMatrix(
{
origins: [origin],
destinations: [destination],
travelMode: google.maps.TravelMode.DRIVING,
unitSystem: google.maps.UnitSystem.METRIC,
avoidHighways: false,
avoidTolls: false
}, function (response, status) {
if (status != google.maps.DistanceMatrixStatus.OK) {
$('#result1').html(err);
}
else
{
var origin = response.originAddresses[0];
var destination = response.destinationAddresses[0];
if (response.rows[0].elements[0].status === "ZERO_RESULTS") {
$('#result1').html("No result for this search");
}
else
{
var distance = response.rows[0].elements[0].distance;
var distance_value = distance.value;
var distance_text = distance.text;
var kms = distance_text.substring(0, distance_text.length - 3);
//$('#result1').html("Result = " + kms);
// console.log("distance result a " + kms);
if(typeof ref_Callback_calcDistance === 'function'){
ref_Callback_calcDistance(kms)
}
}
}
});
}
function Callback_calcDistance(kms) {
distanceResult1 = kms;
if ((calcD < 2000) && (distanceResult1 <= extra_dist)) {
console.log("distanceResult1 <= extra_dist & calD" + data[i].ride_id);
output1 +=
"<tr><td class='tablehdr-15'>" +
data[i].ride_id +
"</td><td class='tablehdr-60'><a href='includes/ridedetails.inc.php?rideid=" + data[i].ride_id + "' target='_blank'>" +
data[i].dest_address +
"</a></td><td class='tablehdr-25'>" +
data[i].ride_time +
"</td></tr>";
$("#result1").html(output1);
$("#infotext").html("The following rides meet your search criteria. Click on the ride to get more information");
} else {
//$("#result").html("<p class='loginError' >No Rides match your Search</p>");
}
}
}
var output2 = "</tbody></table>";
$("#result2").html(output2);
//$("table").addClass("table-300");
}
},
error: function(e) {
console.log(e.message);
}
});
event.preventDefault();
});
});
</script>
<div class="main-wrapper">
<h3 class="h3-heading">Find Ride</h3>
<form class="form-wrapper" id="findride" action="includes/findride.inc.php" method="post">
<p class="pTextsm">Date of Travel</p>
<input class="def-form" type="date" id="rdate" name="rdate"><br>
<p class="pTextsm">Arrival Time at Destination</p>
<input class="def-form" type="time" id="rtime" name="rtime" value="12:00"><br>
<p class="pTextsm">Seats required</p>
<input class="def-formB" type="text" id="seatsreq" name="seatsreq"><br>
<p class="pTextsm">Destination Address (if no result enter surburb and map will display. Then place marker to get address) </p>
<input class="def-form" type="text" id="autocomplete" onFocus="geolocate()" name="address"><br>
<div id="maprd" style="display: none;"></div>
<!-- <p class="pTextsm">Pick up Address</p>
<p class="pTextsm" id="addresspickupdef"></p>
<p class="pTextsm">(enter only if different from your Account Address)</p>
<input class="def-form" type="text" id="autocompletepickup" onFocus="geolocate()" name="pickupaddress"><br> -->
<input type="hidden" id="place_id" name="place_id" value="test">
<input type="hidden" id="lat" name="lat">
<input type="hidden" id="lng" name="lng">
<input type="hidden" id="place_idpickup" name="place_idpickup" value="test">
<input type="hidden" id="latpickup" name="latpickup">
<input type="hidden" id="lngpickup" name="lngpickup">
<!-- <input type="hidden" id="seatsreq" name="seatsreq"> -->
<input type="hidden" id="latlngnew" type="text" value="40.714224,-73.961452">
<button class="def-form-button" type="submit" id="ridesub" name="ridesub">Find Ride</button>
</form>
<div id="infotext"></div>
<div id="result"></div>
<div id="result1"></div>
<div id="result2"></div>
<div id="norides"></div>
<div id="placeidshow"></div>
<div id="latsdiv"></div>
<div id="lngsdiv"></div>
<div id="latdbdiv"></div>
<div id="lngdbdiv"></div>
<div id="calcDdiv"></div>
<div id="calcseatsavail"></div>
<div id="seatsreq1"></div>
</div>
</main>
<script>
var placeSearch, autocomplete, autocompletepickup, placeId, placeIdpickup;
function initAutocomplete() {
autocomplete = new google.maps.places.Autocomplete(
/** @type {!HTMLInputElement} */(document.getElementById('autocomplete')),
{types: ['geocode']});
autocomplete.setComponentRestrictions(
{'country': ['nz']});
autocomplete.addListener('place_changed', fillInAddress);
autocompletepickup = new google.maps.places.Autocomplete(
/** @type {!HTMLInputElement} */(document.getElementById('autocompletepickup')),
{types: ['geocode']});
autocompletepickup.setComponentRestrictions(
{'country': ['nz']});
autocompletepickup.addListener('place_changed', fillInAddresspickup);
}
function fillInAddress() {
var place = autocomplete.getPlace();
var lat = place.geometry.location.lat();
var lng = place.geometry.location.lng();
document.getElementById('lat').value = lat;
document.getElementById('lng').value = lng;
placeId = place.place_id;
document.getElementById('place_id').value = placeId;
$("#maprd").css("display", "block");
myMap(lat,lng);
//$('#placeidshow').html(lat);
}
function fillInAddresspickup() {
var place = autocompletepickup.getPlace();
var lat = place.geometry.location.lat();
var lng = place.geometry.location.lng();
document.getElementById('latpickup').value = lat;
document.getElementById('lngpickup').value = lng;
placeId = place.place_id;
document.getElementById('place_idpickup').value = placeId;
//$('#placeidshow').html(lat);
}
function geolocate() {
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(function(position) {
var geolocation = {
lat: position.coords.latitude,
lng: position.coords.longitude
};
var circle = new google.maps.Circle({
center: geolocation,
radius: position.coords.accuracy
});
autocomplete.setBounds(circle.getBounds());
});
}
}
</script>
<script>
var map, marker, newmarker, geocoder, infowindow, newmarkerlat, newmarkerlng;
function myMap(lat,long) {
var myCenter = new google.maps.LatLng(lat,long);
var mapCanvas = document.getElementById("maprd");
var mapOptions = {
center: myCenter,
zoom: 18
// streetViewControl: false,
// mapTypeControl: false
};
map = new google.maps.Map(mapCanvas, mapOptions);
marker = new google.maps.Marker(
{
position:myCenter,
draggable: true
}
);
marker.setMap(map);
google.maps.event.addListener(marker,'click',function() {
//map.setZoom(12);
map.setCenter(marker.getPosition());
});
google.maps.event.addListener(map, 'click', function(event) {
newmarkerlat = event.latLng.lat();
newmarkerlng = event.latLng.lng();
var newmarkerlatlng = "" + newmarkerlat + "," + newmarkerlng;
document.getElementById('latlngnew').value = newmarkerlatlng;
placeMarker(map, event.latLng);
// console.log(document.getElementById('latlngnew').value);
});
}
function placeMarker(map, location) {
var marker = new google.maps.Marker({
position: location,
map: map
});
infowindow = new google.maps.InfoWindow;
geocoder = new google.maps.Geocoder;
geocodeLatLng(geocoder, map, infowindow);
}
function geocodeLatLng(geocoder, map, infowindow) {
var input = document.getElementById('latlngnew').value;
var latlngStr = input.split(',', 2);
var latlng = {lat: parseFloat(latlngStr[0]), lng: parseFloat(latlngStr[1])};
geocoder.geocode({'location': latlng}, function(results, status) {
if (status === 'OK') {
if (results[0]) {
//map.setZoom(11);
var marker = new google.maps.Marker({
position: latlng,
map: map
});
infowindow.setContent(results[0].formatted_address);
infowindow.open(map, marker);
document.getElementById('autocomplete').value = results[0].formatted_address;
} else {
window.alert('No results found');
}
} else {
window.alert('Geocoder failed due to: ' + status);
}
});
}
</script>
for语句中的异步回调=recursiontry for let i in datainstead@RemisaYousefvand不，递归与异步无关，回调也与loopshow无关。你是为了防止递归吗？@feaseyweis没有递归，所以没有什么可以防止的。。。尝试使用let而不是var的最简单解决方案。。。您遇到的问题是，在异步代码调用回调后，我将不会是您所期望的那样-但是，使用let，它将完全是您所期望的，因为letI的块范围尝试了这一点。由于getDistanceMatrix异步运行，在代码完成之前不会返回结果，因此kms在分配kms值后仍然显示为未定义的检查回调\u calcDistance函数调用。我可以通过回调函数Callback\u calcDistancekms访问kms，并通过console进行检查。logdistanceResult+kms；但是不能从回调中得到它。Callback\u calcDistancekms函数调用了引用参数函数ref\u Callback\u calcDistancekms右，我认为是另一种方式？？Callback_calcDistancekms通过ref_Callback_calcDistancekms传递