JSEval

Notice: Conclusion of the JSEval Experimental Plugin

Date: July 1, 2026

Subject: End of the JSEval experiment and next steps

We have officially concluded our JSEval experiment, which was downloaded by 75 users between May and June 2026. Thanks to your participation, we gained valuable insights into how developers interact with this tool. Based on our findings, there is no value in continuing JS Eval in its current form, given the evolving patterns of how developers engage with AI agents.

Consequently, the JSEval experimental plugin will be removed from the JetBrains Marketplace in August 2026.

What’s next?

While the plugin is being retired, the underlying technology is not. We are actively researching how to reuse the technology behind JSEval to support agentic debugging turns, enabling more efficient, agentic debugging workflows directly inside WebStorm.

We value your feedback

To help shape our future debugging tools, please share your experience with us by completing our brief, anonymous feedback form:

https://forms.gle/KCBCVTjic2stZcXn8

Thank you for helping us innovate and improve the WebStorm ecosystem!

With the JSEval plugin you can inspect the evaluation results of your code exactly at the position they appear in a JavaScript or a TypeScript file. The tool allows for inspecting values from console.log expressions as well as from expressions with appended //= comments before an expression is reached.

Additionally, you can further change the context of the execution by selecting a runtime, specifying environment variables and application parameters, configuring TypeScript handling, and more.

Before you start

Make sure you are using WebStorm version 2026.1.1 or later.

Install the JSEval plugin

Press Ctrl+Alt+S to open settings and then select Plugins.
Open the Marketplace tab, locate the JSEval plugin in the list and click Install.

Live evaluations and code coverage

With JSEval, you can inspect your code on the fly, receiving live updates to evaluations and code coverage as your program is executing. The value of an expression is visible in the editor directly when it becomes available or is executed.

Mark expressions to evaluate

Append a //= comment at the end of an expression that you want to be evaluated.
To use another character string, open settings Ctrl+Alt+S, go to Tools | JSEval, and then specify the desired character string in the Report comment field.
Alternatively, log the value to the console by using one of the following error methods:
- console.log()
- console.error()
- console.trace()
- console.info()
- console.debug()
- console.warn()

Start evaluation

Open the file to evaluate in the editor.
From the main menu, select View | Tool Windows | JSEval to open the JSEval tool window.
In the JSEval tool window, do one of the following:
- Click on the toolbar and select the file to evaluate from the list.
- To evaluate the file in the currently active editor tab, click .
A new tab with the name of the inspected file is added to the JSEval tool window where the values of the expressions marked for evaluation are shows. The values are also displayed right in the editro, next to the corresponding expressions.

Error tracing

When execution of a file fails, JSEval displays an error trace, so you can clearly see where the error comes from.

JSEval tool window

Every expression that is evaluated and presented can be further inspected in the dedicated JSEval tool window. Here you can also inspect the deeply nested elements of objects and arrays and copy the values from the tree. Double-clicking an item leads to the point where it is evaluated from.

Tracking time passed

Use the //' comment to track how long it took to reach a specific expression from the execution start.

Support for imports

You can also track files with imports from packages or other project files. Values are updated on changes in the imported files.

Configuring the context of executions

Choose a runtime for executions

When executing your code, you can switch between various Node.js runtime versions to explore differences between them.

Configure TypeScript handling

For TypeScript files, you can also configure TypeScript transpilation handling for Node.js.

From the drop-down list on the toolbar of the JSEval tool window, select one of the following options:

Default TS Handling - with this option selected, no TypeScript handling is added. You can still configure custom handling through advanced file settings as described above.
Transform Types - select this option to have --experimental-transform -types appended to the Node.js parameters. Transformation is applied to TypeScript-only types, such as, enum and namespace.
With Node.js 26.0.0 and later, this tag is no longer available.

Configure additional execution properties

You can additionally specify the parameters to be passed to the runtime or to the application, the working directory to run the application in, as well as the environment variables.

Specify advanced evaluation control settings

In the JSEval tool window, click .
In the Advanced File Evaluation Control dialog that opens specify the additional configuration settings

Configure the appearance of evaluation reports

To change the default style of evaluation reports and time evaluation reports, press Ctrl+Alt+S to open settings, go to Editor | Color Scheme | JSEval, and configure the styles and colors according to your preferences. Check the new appearance in the Preview area.

07 July 2026