在ArcGIS中，可以使用SpatialReference、Graphic、geometryEngine和query相关类来查找距离给定点最近的点。

以下是一个示例代码，其中包含一个示例geoJSON多点要素数组和一个用于查找最近点的函数findClosestPoint：

require([
  "esri/geometry/Point",
  "esri/tasks/GeometryService",
  "esri/tasks/support/ProjectParameters",
  "esri/geometry/geometryEngine",
  "esri/Graphic",
  "dojo/domReady!"
], function(Point, GeometryService, ProjectParameters, geometryEngine, Graphic) {

  // GeoJSON multi-point feature example
  var multiPointFeature = {
    "type": "Feature",
    "geometry": {
      "type": "MultiPoint",
      "coordinates": [
        [0, 0],
        [2, 2],
        [4, 4],
        [6, 6]
      ]
    }
  };

  // Function to find closest point to given point in multi-point feature
  function findClosestPoint(point, multiPointFeature) {
    // Project point to spatial reference of multi-point feature
    var geometryService = new GeometryService("https://utility.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer");
    var projectParameters = new ProjectParameters({
      geometries: [point],
      outSR: multiPointFeature.geometry.spatialReference
    });
    geometryService.project(projectParameters).then(function(result) {
      // Find closest point using geometryEngine.nearestCoordinate
      var closestPoint = geometryEngine.nearestCoordinate(multiPointFeature.geometry, result[0]);
      // Create a graphic for the closest point and add it to the map
      var graphic = new Graphic({
        geometry: closestPoint.coordinate,
        symbol: {
          type: "simple-marker",
          style: "square",
          color: "blue",
          size: "12px",
          outline: {
            color: [255, 255, 0],
            width: 3
          }
        }
      });