我正在使用KnockoutJS库开发一个简单的Google Maps应用-至少在概念上似乎足够简单。
在阅读了KnockoutJS并编写了一些示例之后，我整理了初始部分。到目前为止的html只是地图，我的目标是在克服第一个障碍后立即填充列表。障碍在Javascript中。这是供参考的代码：
"use strict";
var map;
var center;
var defaultBounds;
var placesServices;
//LocationObject created to hold data for locations generated from google.places.nearbySearch
var LocationObject = function(data){
this.position = data.geometry.location;
this.lat = data.geometry.location.lat;
this.lng = data.geometry.location.lng;
this.name = data.name;
this.placeID = data.place_id;
this.rating = data.rating;
this.types = data.types;
this.linkToPhoto = data.html_attributions;
};
function initMap(){
map = new google.maps.Map(document.getElementById('map'), {
center: center,
zoom: 17,
mapTypeId: 'satellite',
draggable: true,
zoomControl: false,
scrollwheel: true,
disableDoubleClickZoom: true
});
defaultBounds = new google.maps.LatLngBounds(
new google.maps.LatLng(47.614217, -122.317981),new google.maps.LatLng(47.612975, -122.316291));
map.fitBounds(defaultBounds);
placesServices = new google.maps.places.PlacesService(map);
}
//ViewModel created to observe changes on the map
var MapViewModel = function(){
var self = this;
self.testarr = ko.observableArray([
{ firstName: 'Bert', lastName: 'Bertington' },
{ firstName: 'Charles', lastName: 'Charlesforth' },
{ firstName: 'Denise', lastName: 'Dentiste' }
]);
self.locations = ko.observableArray([]);
self.markers = [];
this.getNearbyLocations = function(){
if(placesServices === undefined){
placesServices = new google.maps.places.PlacesService(map);
}
var request = {
location: center,
radius: getBoundsRadius(defaultBounds),
type: ['establishment']
};
placesServices.nearbySearch(request, function(results, status) {
if (status === google.maps.places.PlacesServiceStatus.OK) {
for (var i = 0; i <= 18; i++) {
var marker = new google.maps.Marker({
map: map,
position: results[i].geometry.location,
animation: google.maps.Animation.DROP
});
self.locations.push(new LocationObject(results[i]));
self.markers.push(marker);
}
} else{
alert("We were not able to find any nearby locations in this Neighbourhood.");
}
});
};
this.init = function(){
self.getNearbyLocations();
};
};
var myMapViewModel = new MapViewModel();
myMapViewModel.init();
ko.applyBindings(myMapViewModel);
/* Utility Functions */
function getBoundsRadius(bounds){....}
错误是：
Uncaught ReferenceError: google is not defined
at MapViewModel.getNearbyLocations
而且我不明白为什么在地图本身首先加载而没有问题但在这里挂起时却无法在这里识别它的原因。
这是供参考的html，但那里应该没有问题：
<!DOCTYPE html>
<html lang="en">
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<!-- Per Google guideline scheduled for the M65 release, css has been moved to an importer -->
<link rel="import" href="importer.htm"></link>
<!-- Bootstrap CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" integrity="sha384-/Y6pD6FV/Vv2HJnA6t+vslU6fwYXjCFtcEpHbNJ0lyAFsXTsjBbfaDjzALeQsN6M" crossorigin="anonymous">
</head>
<body>
<div class="container-fluid">
<div class="row">
<div class="col-xs-12 col-md-4">
<!-- List goes in this column. -->
</div>
</div>
<div class="col-xs-12 col-md-8">
<!-- Map goes into this column. -->
<div id="map" style="width:100%;height:100vh;"></div>
</div>
</div>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.11.0/umd/popper.min.js" integrity="sha384-b/U6ypiBEHpOf/4+1nzFpr53nxSS+GLCkfwBdFNTxtclqqenISfwAzpKaMNFNmj4" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/js/bootstrap.min.js" integrity="sha384-h0AbiXch4ZDo7tp9hKZ4TsHbi047NrKGLO3SEJAg45jXxnGIfYzk4Si90RDIqNm1" crossorigin="anonymous"></script>
<!-- Optional JavaScript -->
<script src="js/knockout.js" ></script>
<script src="js/app.js"></script>
<script async defer src="https://maps.googleapis.com/maps/api/js?key=AIzaSyC-1EdIyUOb74oGG_mEoPvJTAGCSJvSQms&callback=initMap&libraries=places"></script>
</body>
最佳答案
我还认为错误是因为在maps脚本之前调用了app.js。但是我尝试更改它，这是同样的错误，并且我还尝试删除async参数（如user3297291的注释所建议），仍然是相同的错误。理论上是should have worked。
但这可行-将app.js代码的最后3行包装在ready()函数中：
$(document).ready(function(){
var myMapViewModel = new MapViewModel();
myMapViewModel.init();
ko.applyBindings(myMapViewModel);
});
关于javascript - KnockoutJS中的ViewModel无法访问全局变量，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/46659746/