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Cross Origin Resource Sharing (CORS) - buffer


This sample is experimental and may not work on all browsers. Visit caniuse.com to determine if the CORS capabilities used in this sample are available for your browser.

Cross-Origin Resource Sharing (CORS) allows web applications to bypass a browser's same origin policy. When both the web server and browser support CORS, a proxy is not required to do cross-domain requests. This both simplifies application development and potentially provides a performance boost. Development is simplified because it is no longer necessary to maintain a proxy page on your server. The performance boost comes from accessing a resource directly rather than sending a request back to your server, which then requests the specified URL and returns the result.

To use CORS from an ArcGIS API for JavaScript application, add the root URL for CORS enabled servers to
, which is an array of strings. As stated previously, web servers must be pre-configured to support CORS. This is a straightforward, simple process and enable-cors.org has walkthroughs on how to enable CORS for popular web servers.

This sample shows simplify and buffer operations for a large polygon running without a proxy when running in browsers that support CORS. If a browser does not support CORS, this sample falls back to using a proxy.


<!DOCTYPE html>
    <meta charset="utf-8">
    <meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no">
    <title>Cross Origin Resource Sharing (CORS) - buffer</title>
    <link rel="stylesheet" href="https://js.arcgis.com/3.20/esri/css/esri.css">
      html, body, #map { height: 100%; width: 100%; margin: 0; padding: 0; }
      #controls {
        position: absolute;
        bottom: 20px;
        left: 20px;
        z-index: 40;
        width: 240px;
        height: 70px;
        background: #fff;
        color: #000;
        padding: 5px;
        font-family: arial;
        -moz-box-shadow: 0 0 5px #888;
        -webkit-box-shadow: 0 0 5px #888;
        box-shadow: 0 0 5px #888;

    <script src="javascript/graphics.js"></script>
    <script src="https://js.arcgis.com/3.20/"></script>
      var map, graphics, gs, ela = {};
        "esri/map", "esri/tasks/GeometryService",
        "esri/SpatialReference", "esri/tasks/BufferParameters", "esri/config",
        "esri/symbols/SimpleFillSymbol", "esri/symbols/SimpleLineSymbol",
        "esri/graphic", "esri/layers/GraphicsLayer",
        "esri/Color", "dojo/_base/array",
        "dojo/on", "dojo/dom", "dojo/parser", "dojo/domReady!"
      ], function(
        Map, GeometryService,
        SpatialReference, BufferParameters, esriConfig,
        SimpleFillSymbol, SimpleLineSymbol,
        Graphic, GraphicsLayer,
        Color, arrayUtils,
        on, dom, parser
      ) {

        // fallback to proxy for non-CORS capable browsers
        esriConfig.defaults.io.proxyUrl = "/proxy/";

        // graphic to be simplified then buffered
        // g1 and g2 are JSON from graphics.js
        graphics = { simple: g2, complex: g1 };

        // set up geometry service
        gs = new GeometryService("https://utility.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer");

        map = new Map("map", {
          basemap: "topo",
          center: [-113.302, 41.384],
          zoom: 7,
          logo: false,
          slider: false

        var bufferGraphics = new GraphicsLayer({ id: "bufferGraphics" });

        map.on("load", function() {
          // add the graphic to the map
          map.getLayer("bufferGraphics").add(new Graphic(graphics.complex));
          on(dom.byId("buffer"), "click", buffer);
          on(dom.byId("graphicSel"), "change", updateGraphic);

        function buffer() {
          dom.byId("ela").innerHTML = "Buffering...";
          var bufferGraphics = map.getLayer("bufferGraphics");
          arrayUtils.forEach(bufferGraphics.graphics, function(g) {
            if ( g.attributes && g.attributes.hasOwnProperty("buffer") ) {

          // used for timing
          if ( ela.hasOwnProperty('start') ) {
            delete ela.start;
            delete ela.end;
          ela.start = new Date().getTime();

          var params = new BufferParameters();
          params.distances = [ 25 ];
          params.bufferSpatialReference = new SpatialReference({ wkid: 102100 });
          params.outSpatialReference = map.spatialReference;
          params.unit = GeometryService.UNIT_STATUTE_MILE; // 9093
          gs.simplify([bufferGraphics.graphics[0].geometry], function(geometries) {
            params.geometries = geometries;
            gs.buffer(params, showBuffer);
        function showBuffer(bufferedGeometries) {
          ela.end = new Date().getTime();
          dom.byId("ela").innerHTML = (ela.end - ela.start) + "ms";

          var symbol = new SimpleFillSymbol(
            new SimpleLineSymbol(
              new Color([255,0,0,0.65]), 2
            new Color([255,0,0,0.35])

          arrayUtils.forEach(bufferedGeometries, function(geometry) {
            var graphic = new Graphic(geometry, symbol, { buffer: true });
        function updateGraphic(e) {
          var bufferGraphics = map.getLayer("bufferGraphics");
          bufferGraphics.add(new Graphic(graphics[e.target.value]));

    <div data-dojo-type="dijit/layout/BorderContainer"
         style="width: 100%; height: 100%; margin: 0;">
      <div id="map"

        <div id="controls">
          Select graphic:
          <select id="graphicSel">
            <option value="simple">simple</option>
            <option selected value="complex">complex</option>
          Elapsed time: <span id="ela">N/A</span>
          <button id="buffer">Buffer Graphic</button>