JS Objects
Writing extensive code without a full-fledge editor could be challenging. The JavaScript Editor(beta) in Appsmith allows you to create a reusable set of JavaScript functions that you can call within JavaScript bindings across a Page’s component to write complex code with ease. In Appsmith, it’s referred to as JS Objects.

JS Object

A JS Object is an entity comprised of multiple functions and variables. It is a reusable component you can refer to in other JS Objects, allowing you to create a neatly organized set of hierarchies.
How to Create a JS Object?
You can create new JS Objects from the Entity Explorer.
Navigate to Entity Explorer >> Click (+) next to Queries/JS >> Select New JS Object.
How to add a JS Object?
The screen below shows a JS Object added to the page. The default code template that supports export default.
When you add a new JS Object
  1. 1.
    Give a meaningful name to the JSObject
  2. 2.
    Code editor where you can write JavaScript Code
  3. 3.
    Settings are available for Async functions only.
  4. 4.
    Define variables
  5. 5.
    Define functions
  6. 6.
    Use the editor to do several jobs, to name a few:
    1. 1.
      Write your code
    2. 2.
      Call in-built or user-defined functions
    3. 3.
      API calls
    4. 4.
      Database query execution
  7. 7.
    Add multiple functions to the JS Object
  8. 8.
    Access JS Objects from Explorer available under JS Objects Group
The support for the named exports is not available for exporting functions. However, you can expose functions that are part of the JS Object using default export.

Calling a JS Object Function

You can call the functions defined in a JS Object by using the notation {{ JS_OBJECT_NAME.Function_Name }} embedded in a mustache sign as shown in the figure below:
How to call a function defined in a JS Object?
The JS Objects defined are available across APIs, Queries, or other JS Objects defined for a particular page, i.e., the JS Objects have page-level access and are not accessible across pages.

Types of JS Functions

You can write different types of functions in a JS Object that can be Synchronous or Asynchronous.

Synchronous

As the name suggests, synchronous means to be in a sequence, i.e., every statement of the code gets executed one by one. So, a statement must wait for the earlier statement to complete its execution.
For example, the below code snippet shows a data filter:
Api.data.filter(() => {}); // filtering data
Here data filtering is the process of selecting a subset of data you want to choose for viewing or analysis. To filter the data, you must traverse the whole dataset one after the other and segregate it if it matches the filter criteria. Thus, you need synchronous execution.

Asynchronous

The word asynchronous means not occurring at the same time. You may sometimes need to fetch data from the server or execute a function with a delay, something you do not anticipate occurring at the current time.
For example, Promises, Api.run(), Query.Run(), Appsmith platform functions(eg. showModal). It basically lets you delay the execution of code embedded in an async function and is executed when needed.
You can configure additional settings for the asynchronous function and enhance the user experience.

Working with JavaScript Editor

JavaScript Editor is an extensive editor that provides additional functionalities while writing code. You can do a lot with it, like:
A quick walkthrough of JavaScript Editor
What do you get?
Description
Response Tab
Execute each function at the time of development and view the output in the Response tab
Linting Errors
Get the linting errors caught right in the editor
Errors Tab
Check for the syntax errors in the Errors tab
Logs Tab
Check the function execution log in the Logs tab
Snippets
Insert ready-to-use snippets
Debugger Statements
Use debugger statements to pause the execution
To understand how JavaScript Editor works, let’s create a Hello World JS Object.
  • Navigate to Explorer >> Click (+) for Queries/JS >> Select New JS Object.
  • You’ll see the default code template. Add the below code snippet:
export default {
hello: () => {
return “Hello World”;
}
}

Response Tab

The response tab displays the output generated by the functions defined in a JS Object.

Execute Function

You can click Run available on the top right corner to execute the JS function. If your JS object has only one function defined, the editor defaults the function name. But if your JS Object has more than one function defined, you can select the function you want to execute and then click Run.
Response Tab
If your code has syntax errors, the Run button is disabled and blocks the execution. You can resolve the errors and then execute the function using Run.
You can verify the response generated by the hello() in the Response tab, as shown in the screenshot above.
You can execute the function by clicking the RUN button or by using a shortcut key (CMD+ENTER or CTRL + ENTER)

Linting Errors

The Javascript Editor automatically checks your source code for programmatic errors. If the code is not programmatically correct, it will highlight the error using a red-colored lint below the erroneous code. For example, the syntax error where the return is misspelled as retu is also captured by linting.
Linting also captures the Syntax error and highlights it with a red line below it.
You can inspect the error in detail from the Errors tab.

Errors Tab

The errors tab displays all types of errors generated by the code execution. The errors could be comprised of Syntax Errors, Run time errors like Parsing Errors, and more.
Errors Tab

Logs Tab

The Logs tab shows the execution of functions with a timestamp. You can also open the Logs Tab by clicking a debug icon at the right bottom of the console (as shown in the screenshot below).
Logs Tab
The logs tab gives you the flexibility to filter logs either by writing keywords in the Filter box or selecting the type of log from the dropdown.

Snippets

You’ll see a Snippets button available on the right top side of the editor. Click on it to open the Appsmith Snippet Library.
Snippets Button

Appsmith Snippet Library

You can search and copy the Snippets from the Appsmith Snippet Library and use them in the JavaScript Editor. You can then build on the code snippet to add your code or use it as is.
Appsmith Snippet Library
Appsmith is actively working on expanding the Snippets Library. Please reach out to us on Discord or Community Forms if you wish to contribute to the library.

Debugger Statements

The debugger statement in JavaScript will help you pause the code execution during the development phase. The debugger lets you visualize the data and operations when executed on runtime.
You’ll have to use the debugger keyword in the code snippet to pause the execution.
You must have the browser’s developer console open to see the debugger in action.
How to use Debugger statements in JavaScript Editor?
For example, you are returning user information fetched from the userDetailsAPI in the JS function, and you want to see the value returned by the API during execution. To get this working, you can use a debugger statement as below:
export default {
getUserDetails: async () => {
const userInfo = await userDetailsAPI.run();
debugger; // the execution will be paused at this point
// and you can check the value of the userInfo variable
console.log(“user information: “+userInfo); // the logs will be
// printed in the browser
// console.
return userInfo;
}
}

Writing Complex Code

When you build applications, it’s often more than just a CRUD operation from a single datasource. You might integrate with multiple APIs or want to have the dataset created by querying multiple tables, which leads to traversing data, filtering, or manipulating the response by calling different APIs. You can write complex logic with ease using JavaScript Editor.
To understand it further, let’s look at a use case and build different workflows.

Use case

You want to create a developer task tracker dashboard, update developer information, and add some permissions like making sure only admins can access the dashboard.

Code Workflow

Let’s create a task tracker dashboard that gives you an overview of progress on tasks. You have a query called “developers,” which fetches the developers’ information like name, email, etc. You have an API getAllDeveloperTaskStatus that gives you a task list with the status for each developer.
Task Tracker
You want to display the developer details in a tabular format so that you can choose a table widget. You would want to show a total number of tasks like total tasks, no of completed tasks, no of to-do tasks, and no of in-progress tasks. You can achieve this by adding a JS Object and creating one function in it, “getTaskList.” Let’s write the code for this function using the JavaScript Editor.
  • In the Explorer tab, >> click (+) next to JS Objects >> Select New JS Object.
  • It’ll open a JS Editor. Rename the JS Object to Utils
  • Add the below code snippet in the Code tab.
export default {
getAllDeveloperTaskStatus: () => {
return developers.data.map((developer) => {
const developerId = developer.id;
const taskList = developerTaskStatus.data.filter((alltask) => alltask.userId === String(developerId)); // fetch all the tasks for the given developer
const completedTaskList = taskList.filter((task) => task.status === "Completed"); // fetch tasks that are completed by the developer
const todoTaskList = taskList.filter((task) => task.status === "To-Do"); // fetch tasks that are not yet started by the developer
const inProgressTaskList = taskList.filter((task) => task.completed === "In-Progress"); // fetch tasks that are in progress by the developer
return {
"Id": developer.id,
"Name": developer.name,
"Email": developer.email,
"Total Tasks": taskList.length,
"To-Do Tasks": todoTaskList.length,
"In Progress Tasks": inProgressTaskList.length,
"Completed Tasks": completedTaskList.length
};
})
}
}
The getAllDeveloperTaskStatus function does the following:
  • Reads all the developers’ data
  • Iterates for each developer record
    • Scans the tasklist to fetch the developer-related tasks
      • Based on task status (TO-DO, In-Progress, and Completed)
    • Generate a response that gives a cumulative task breakup for each task status for each developer
To display the response generated bygetAllDeveloperTaskStatus we'll bind it to a widget.
  • Navigate to Page >> Select Table widget in Widgets Tab >> Drag it onto the canvas.
  • Select the Table Widget on the canvas
  • In the Property Pane on right side add the code {{Utils.getAllDeveloperTaskStatus()}} in Table Data property.
Add a Table Widget to display data
The table widget will show the data as shown in the below screenshot.
Display data in a table widget
Update Developer Information
Let’s add another function where you’ll be able to select a developer record and update the information.
To achieve this, add a new column to the table widget and select the Column Type as an icon button type that will open a modal window.
How to add an edit column to the table widget?
Now that the Edit column is added to the table let’s add a modal to fetch the developer information like Name and Email.
How to add a modal to edit a developer's details?
Navigate to Explorer >> Select Utils >> Add the code snippet for updateUserData() after getAllDeveloperTaskStatus().
export default {
getAllDeveloperTaskStatus: () => {
...// code block for getAllDeveloperTaskStatus
},
updateUserData: () => {
// Construct new user's data
const newUserData = {
...Table1.selectedRow,
name: devName.text,
email: devEmail.text,
}
// Run updateDeveloperDetails query
updateDeveloperDetails.run(
// on successful execution of updateDeveloperDetails run developers to fetch updated data
async () => {
await developers.run();
closeModal("editModal");
showAlert("Developer Details are updated successfully!");
},
// On Error, close the modal and show an error toast
(e) => {
closeModal("editModal")
showAlert("An error occurred while updating the developer details!");
if (e.statusCode === 401) {
navigateTo("Page1");
}
},
// Params Object
newUserData)
}
}
The updateUserData function does the following:
  • Create the dynamic data that is updated by the user in editModal in newUserData JSON
  • Executes query updateDeveloperDetails
    • On successful execution of the query:
      • Calls developers query to fetch the updated developer details
      • Shows a success toast to the user
      • Closes the editModal
    • On error or failed execution of the query
      • Shows an error toast to the user
      • Closes the editModal
Rename the Confirm button to Update and bind the function updateUserData to its onClick() event. You can bind the function call by using {{Utils.updateUserData()}}.
How to bind function call to an onClick event?
When you'll hit the Update button, the updateUserData function gets executed that updates the developer information and refreshes the developer table to fetch the updated information.
Add Permissions
As you want only the admins to access the Dashboard, let’s create another function for access control. The function will contain a list of users’ emails who will have access to update data in the table. Let’s call this function isAdmin.
Add the code snippet for isAdmin() and adminsList to the Utils JS Object.
export default {
getAllDeveloperTaskStatus() => {
... // code block for getAllDeveloperTaskStatus
},
updateUsersData() => {
... // code block for updateUserData
},
isAdmin: (email) => {
if (this.adminList.indexOf(appsmith.user.email) > -1) { // check if the logged in user is an admin
return true;
}
return false;
}
}
The final function will look as below:
export default {
//the allowed list of admin's email
getAllDeveloperTaskStatus: () => {
return developers.data.map((developer) => {
const developerId = developer.id;
const taskList = developerTaskStatus.data.filter((alltask) => alltask.userId === String(developerId)); // fetch all the tasks for the given developer
const completedTaskList = taskList.filter((task) => task.status === "Completed"); // fetch tasks that are completed by the developer
const todoTaskList = taskList.filter((task) => task.status === "To-Do"); // fetch tasks that are not yet started by the developer
const inProgressTaskList = taskList.filter((task) => task.completed === "In-Progress"); // fetch tasks that are in progress by the developer
return {
"Id": developer.id,
"Name": developer.name,
"Email": developer.email,
"Total Tasks": taskList.length,
"To-Do Tasks": todoTaskList.length,
"In Progress Tasks": inProgressTaskList.length,
"Completed Tasks": completedTaskList.length
};
})
},
updateUserData: () => {
// Construct new user's data
const newUserData = {
...Table1.selectedRow,
name: devName.text,
email: devEmail.text,
}
// Run updateDeveloperDetails query
updateDeveloperDetails.run(
// on successful execution of updateDeveloperDetails run developers to fetch updated data
async () => {
await developers.run();
closeModal("editModal");
showAlert("Developer Details are updated successfully!");
},
// On Error, close the modal and show an error toast
(e) => {
closeModal("editModal")
showAlert("An error occurred while updating the developer details!");
if (e.statusCode === 401) {
navigateTo("Page1");
}
},
// Params Object
newUserData)
},
isAdmin: async () => {
if (this.adminsList.indexOf(appsmith.user.email) > -1) {
return true;
}
navigateTo("Page2");
return false;
}
}
A user who is not an admin is taken to a no permissions page
Only the users with email added to the adminList will be able to access the dashboard and do the updates.
With the Async function settings, you can bind the isAdmin function to RUN ON PAGE LOAD. The execution of IsAdmin on Page load ensures the validation of the user’s email against the adminList for the logged-in user should happen on the page load. If the logged-in user's email is present in the adminsList, the user can access the Dashboard. If not, the user navigates to the access denied page that shows a message:
You do not have permission to access the Dashboard.

Current Limitations

As the JavaScript Editor is in its BETA, there are a few limitations:
  • At the moment, you cannot use JS Objects across pages. We are working to enable this functionality in the future. You can subscribe to the issue and follow the progress.
  • You cannot define variables and functions outside of export default { }. In future iterations, we will allow you to write and export only selected variables/functions from a JS Object.
Async Function
If a function is async, i.e., if it returns a promise, it cannot be called on the fields incompatible with the return type, such as the default text property of the text widget. For example, in the above screenshot executeQuery returns Api1.run() promise and hence is an async function. You can call executeQuery or similar functions only from trigger or event properties such as OnClick.