Locate SRMP using Arcade

SRMP.arcade.js

/**
 * With LRS layers that are separated by direction, hard-code the direction.
 * For the unified LRS layer, you will need to extract the last character 
 * from the route ID, which includes an "i" or "d" suffix
 */
var direction = "i";

/**
 * Gets the M value of where the user clicked.
 */
function getM() {
  if (TypeOf($userInput) == "Point") {
    var result = PointToCoordinate($feature, $userInput);

    return result.coordinate.m;
  }
  return null;
}

// Get routeID and direction.

function getSrmpInfo() {
  var m = getM();

	Console(`M = ${m}`)

  var routeId = $feature.RouteID;

  /* Milepost fields
  "OBJECTID",
  "RouteID",
  "ARM",
  "SRMP",
  "Direction",
  "Easting",
  "Northing",
  "Longitude",
  "Latitude",
  "Azimuth",
  "StateRouteNumber",
  "RelRouteType",
  "RelRouteQual",
  "AheadBackInd",
  "LRS_Date",

*/

  /** Mileposts layer ArcGIS Online item ID */
  var milepostsItemId = "cb9e130af9374f71a164a9a2d555af96";
  var milepostItemLayerId = 0;
  var milepostsPortal = Portal("https://wsdot.maps.arcgis.com");

  // Round the measure to 2 decimal places.
  var arm = Text(Round(m, 2), "#.00");

  var startTime = Timestamp();

  // Query the mileposts features for features matching the route that
  // was clicked on and measures nearby the measure of the user's click.
  var f = First(
    Filter(
      FeatureSetByPortalItem(
        milepostsPortal,
        milepostsItemId,
        milepostItemLayerId,
        ["RouteID", "Direction", "SRMP", "AheadBackInd", "ARM"],
        false
      ),
      `RouteID = '${routeId}' AND ARM = ${arm} AND Direction IN ('${direction}', 'b')`
    )
  );

  var outputText = "Could not find SRMP";

  if (f != null) {
    

    // Specify the format used when numbers are converted to strings.
    var numberFormat = "#.##";

    // Convert the SRMP to text, and append "B" if it is back mileage.
    var SRMP = Text(f.SRMP, numberFormat);
    if (Upper(f.AheadBackInd) == "B") {
      SRMP = `${SRMP}${f.AheadBackInd}`;
    }

    outputText = SRMP
  }

  // Return output text.
  outputText
}

getSrmpInfo();