fmPromise: a Richer JavaScript Web Viewer Integration

FileMaker 19 has added the ability to call FileMaker scripts from your JavaScript, as well as executing a JavaScript function from a FileMaker script.
This allows for integration between FileMaker and JavaScript/WebViewer, but has some areas that fmPromise will make better.

  • Every call from JavaScript to a FileMaker script needs a public JavaScript function to receive the script response, and it is the responsibility of the Script to call that function.
  • All data coming back from FileMaker is a string
  • Debugging JavaScript errors is very difficult without browser-based dev tools
  • The window.FileMaker object is not available right when the page loads, so you need a window.setTimeout() to wait for it to become available if you want to populate your web viewer using a script call.

fmPromise is designed to address these shortcomings, and help you utilize web viewers in your solution with the minimum amount of fuss.

Long story short, instead of JavaScript like this:

function submitMyOrder(orderDetails) {
  window.progressDialog = showProgressDialog('Submitting...'); // global scope, not ideal const scriptParam = JSON.stringify(orderDetails); // convert JS object to string  
 try {  window.FileMaker.PerformScript('Submit Order from WebViewer', scriptParam); // no return value  
 } catch (e) { showError('Could not call script "Submit Order from WebViewer", was it renamed?" ' + e); }}

// the FileMaker `Submit Order from WebViewer` script is responsible for calling this on success function submitOrderSuccessCallback(payloadString) {  
 const submitResult = JSON.parse(payloadString); // convert string to JS objects  
 showSubmitResult(submitResult);  window.progressDialog.close();

// the FileMaker `Submit Order from WebViewer` script is responsible for calling this on failure function submitOrderErrorCallback(msg) {  
 showError('Could not send order: ' + msg);  window.progressDialog.close();

With fmPromise, the call to fmPromise.performScript() returns a Promise complete with error handling. This lets you write JavaScript like this:

// WITH fmPromise, the call to performScript returns a Promise  
// the `ScriptResult` of `Find Matching Contacts` will be parsed as JSON and used to resolve the Promise  
function submitMyOrder(orderDetails) {
 const progressDialog = showProgressDialog('Submitting...'); // block scope  fmPromise.performScript('Submit Order from WebViewer', orderDetails) // returns a Promise  
 .then(function (submitResult) {
 showSubmitResult(submitResult); }) .catch(function (error) {
 showError('Could not send order: ' + error); }).finally(function () {

Add in the syntactic sugar of async/await and you can have this:

async function submitMyOrder(orderDetails) {
 const progressDialog = showProgressDialog('Submitting...'); try { const submitResult = await fmPromise.performScript('Submit Order from WebViewer', orderDetails);
 showSubmitResult(submitResult); } catch (error) { showError('Could not send order: ' + msg); } finally { progressDialog.close();


I would strongly recommend you enable external JavaScript debugging in your web viewer, as described here

From your terminal, type:

defaults write com.FileMaker.client.pro12 WebKitDebugDeveloperExtrasEnabled -bool YES

This allows you to utilize Safari’s developer tools on your web viewer code, which is incredibly useful.


The FMPromise Add-On workflow is:

  1. Create a new module, which writes my-module.html to your Documents/fmPromise/ directory.
  2. Edit this file and preview it in $$FMPROMISE_DEVMODE
  3. Once satisfied, package the module into the fmPromiseModule table

This packaging step gets the source of your .html file, and optionally inlines any external JavaScript / CSS files.

If you want to change the inline behavior of a script or style, add a data-packageattribute to your <script> or <link> tag containing your JavaScript / CSS.

  • data-package="omit" will remove the tag entirely. This is handy for things which you only want present in dev mode, like Vue Dev Tools.
  • data-package="leave" will not inline the file, but it will remaing as an external resource. This is good for large external libraries, but means your module will probably not work without internet access.


fmPromise.performScript(scriptName, parameter, option) Performs a FileMaker script, returning a Promise. The Promise will be resolved with the script result (parsed as JSON if possible), or rejected if the FileMaker script result starts with the word “ERROR”. The third option parameter specifies how to handle FileMaker scripts which are already running. See FileMaker 19.1.2 release notes for details.

fmPromise.evaluate(expression, letVars) Evaluate an expression in FileMaker using optional letVars. This is also a handy way to set $$GLOBAL variables.

fmPromise.insertFromUrl(url, curlOptions) Inserts from URL without worrying about cross-site scripting limitations imposed on the web viewer.

fmPromise.setFieldByName(url, curlOptions) Sets a field by name in FileMaker.

fmPromise.executeSql(sql, ...bindings) Executes a SQL command with placeholders, parsing the plain-text delimited result into an array of arrays.

Additional benefits

  • FileMaker worker scripts don’t need to know anything about your web viewers, they simply exit with a (preferably JSON) result.
  • FileMaker Scripts can return an “Error …” result, which will be used to reject the script call’s promise.
  • Each FileMaker script call has an id, so you can fire off multiple script calls to FileMaker and they will resolve correctly.
  • You can make script calls as soon as your <script> tag finishes loading, since fmPromisetakes care of polling for the window.FileMaker object.


  • The callback script defaults to looking for a webViewer namedfmPromiseWebViewer. It would be nice if the JavaScript FileMaker object had this as a property. You can override the web viewer name in the JavaScript.
  • When you use Perform Javascript in Web Viewer, you will not get a result if the script your are calling is an async script.

Getting Started

Create a static HTML file and include the fm-promise.js file. Add another<script> block for your own JavaScript. Your script can utilize fmPromiseimmediately on page load to do things like call FileMaker scripts, evaluate expressions, and execute SQL.


<!doctype html>
<html lang="en">
 <meta charset="utf-8"> <script src="fm-promise.js"></script></head>
 'use strict';
 async function hello() {
 const name = await fmPromise.evaluate('Get(Username)');
  document.body.innerText = 'Hello, ' + name; }

Now we want to display this in a Web Viewer in FileMaker.

Add a Web Viewer component to your FileMaker layout. For now, the Web Address can be a file pointing to your HTML file, e.g. "file:///Users/myUserName/MyProject/hello-fmpromise.html".

IMPORTANT: check the box labeled “Allow JavaScript to perform FileMaker Scripts”. Without this step, nothing will happen.

IMPORTANT: in the “Position” inspector, give your web viewer the Name fmPromiseWebViewer.

Now you should be able to go to browse mode and see the hello message displayed.

The following loads vue.js from the internet and then fetches all tables and fields from your FileMaker solution and displays them as nested lists.

<!doctype html>
<html lang="en">
 <meta charset="utf-8"> <script src="fm-promise.js"></script> <script src=""></script> <script> async function fetchSchema() {
 const rows = await fmPromise.executeSql('select tableName, fieldName from filemaker_fields');
 const tables = rows.reduce((result, eachRow) => {
 let tableName = eachRow[0]; let fieldName = eachRow[1]; const tbl = result[tableName] || (result[tableName] = {name: tableName, fields: []});
 tbl.fields.push({name: fieldName});
 return result; }, {});
 new Vue({  el: '#app',
  data: {tables}
 }) }
<div id="app">
 <ol> <li v-for="table in tables"> {{ }} <ul> <li v-for="field in table.fields"> {{ }} </li> </ul> </li> </ol></div></body></html>