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https://github.com/netzmacht/contao-leaflet-libraries.git
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76 lines
3.4 KiB
Markdown
76 lines
3.4 KiB
Markdown
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leaflet-ajax
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===========
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Allows you to call JSON via an Ajax call with a jsonp fallback.
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```javascript
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var geojsonLayer = new L.GeoJSON.AJAX("geojson.json");
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```
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for jsonp add the option "dataType" and set it to "jsonp"
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``` javascript
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var geojsonLayer = L.geoJson.ajax("http:webhost.fake/geojson.jsonp",{dataType:"jsonp"});
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```
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Note that data starts to download when the layer is created NOT when it’s added to the map in order to get a head start.
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You may pass either a url string or an array of url strings if you want to download multiple things (handy
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if your downloading data from an ESRI based thing which will have separate line, point, and poly features).
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As you see you can also use lower case methods without creating new objects
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For weirder jsonp you can set "callbackParam" for if you need to change the name of the callback parameter to something besides "callback", e.g. [Mapquest Nominative Open](http://open.mapquestapi.com/nominatim/) uses "json_callback" instead of "callback".
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If you want to use `eval` to parse JSON in older browsers you need to pass an option `evil` set to something truthy.
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If you want to be able to load stuff from the file system (with appropriate custom flags set) set local to true.
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Gives off three events `data:loading`, `data:progress` and `data:loaded`.
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- `data:loading` fires before we start downloading things, note if the constructor is given a url it won't wait to be added to the map
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to start downloading the data, but it does do an async wait so you have time to add a listener to it (and so [leaflet.spin](https://github.com/makinacorpus/Leaflet.Spin) will work with it).
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- `data:progress` is called each time a file is downloaded and passes the downloaded geojson as event data.
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- `data:loaded` is called when all files have downloaded, this is mainly different from `data:progress` when you are downloading multiple things.
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You can also add a middleware function which is called after you download the data but before you add it to leaflet:
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```javascript
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var geojsonLayer = L.geoJson.ajax("route/to/esri.json",{
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middleware:function(data){
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return esri2geoOrSomething(json);
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}
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});
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```
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addUrl does not clear the current layers but adds to the current one, e.g.:
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```javascript
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var geojsonLayer = L.geoJson.ajax("data.json");
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geojsonLayer.addUrl("data2.json");//we now have 2 layers
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geojsonLayer.refresh();//redownload the most recent layer
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geojsonLayer.refresh("new1.json");//add a new layer replacing whatever is there
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```
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last but now least we can refilter layers without re adding them
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```javascript
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var geojsonLayer = L.geoJson.ajax("data.json");
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geojsonLayer.refilter(function(feature){
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return feature.properties.key === values;
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});
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```
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Behind the scenes are two new classes L.Util.ajax = function (url) for same origin requests and L.Util.jsonp = function (url,options) cross origin ones. Both return promises, which have an additional abort method that will abort the ajax request.
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```js
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L.Util.ajax("url/same/origin.xml").then(function(data){
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doStuff(data);
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});
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//or
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L.Util.jsonp("http://www.dif.ori/gin").then(function(data){
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doStuff(data);
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});
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```
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In related news `L.Util.Promise` is now a constructor for a promise, it takes one argument, a resolver function.
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Some of the jsonp code inspired by/taken from [this interesting looking plugin](https://github.com/stefanocudini/leaflet-search) that I have failed to make heads nor tails of (the plugin, not the jsonp code)
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