---
product: Chilkat
product_version: 11.7.0
language: pascal
language_label: Lazarus Pascal
class: Js
license: bundle
deprecated: false
reference_html: https://www.chilkatsoft.com/refdoc/pascal_JsRef.html
---
# Chilkat Js — Lazarus Pascal — v11.7.0

> Chilkat 11.7.0 · language=pascal · class=Js
> Other versions: replace `11.7.0` in this URL. Other languages: `https://www.chilkatsoft.com/ai-docs/v/11.7.0/<lang>/classes/Js.md`.
> Language-wide rules (install, unlock, error model, strings/bytes): `https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/guide.md`.

## Purpose

**Execute sandboxed JavaScript inside an application with controlled access to Chilkat features.**

Use `Chilkat.Js` when an application needs to execute JavaScript internally while retaining control over what the script is allowed to access. By default, scripts run in a closed sandbox with the JavaScript language and standard library available, but without filesystem, network, or Chilkat class access unless the host application explicitly enables those capabilities.

**Embedded JavaScript engine**

Run JavaScript code from inside the host application without launching an external scripting process.

**Sandboxed by default**

Start from a restricted execution environment and selectively expose only the capabilities the script should use.

**Enable Chilkat classes**

Allow scripts to use selected Chilkat classes when the host application wants JavaScript to perform controlled Chilkat operations.

**Filesystem restrictions**

Optionally restrict filesystem access so scripts can read or write only within approved locations.

**Script input and output**

Execute JavaScript, pass data through the host-controlled environment, and retrieve results or diagnostics from the script run.

**Controlled automation**

Use JavaScript as an embedded extension language for application-defined workflows while keeping host resources protected.

**Common pattern:** Create a `Js` object, load or provide the JavaScript code, enable only the Chilkat classes and filesystem locations the script is permitted to use, run the script, and inspect the result or diagnostic output. Use `Chilkat.Js` when the application needs scriptability with a security boundary controlled by the host.

For an extended overview, see [Js Class Overview](https://www.chilkatsoft.com/js_class_overview.asp). Also see [About the Chilkat.Js JavaScript Engine](https://www.chilkatsoft.com/chilkat_javascript_engine.asp).

**Third-Party Notice** This software includes portions of the QuickJS JavaScript engine. Copyright © 2017–2024 Fabrice Bellard. Licensed under the MIT License. The Chilkat Js engine was originally derived from QuickJS, but has been extensively modified.

## Object creation, unlocking and error handling

**Create / Free**

```pascal
uses
  Chilkat.Js;

var
  obj: TJs;
begin
  obj := TJs.Create;
  try
    if not obj.IsValid then
      raise Exception.Create('Failed to create a TJs instance.');

    // ... use obj ...

  finally
    obj.Free;
  end;
end;
```

`constructor Create;`

Allocates the underlying CkJs object and returns a new TJs instance. Simply adding **Chilkat.Js** to the unit's `uses` clause is enough to locate and bind to the Chilkat shared library (DLL / .so / .dylib) at runtime — no separate load step is required. Check `obj.IsValid` after calling `Create`; it is `False` if the underlying library could not be found/loaded or the object could not be allocated (for example, when unlicensed).

`destructor Destroy; override;`

Every TJs created by calling `Create` should eventually be released by calling `.Free` (inherited from `TObject`). The destructor automatically disposes the underlying CkJs handle. A native (unmanaged) memory leak occurs if the object is never freed.

Call `Global.UnlockBundle` once at the start of the program, before using this or any other Chilkat class. Any string unlocks a fully functional 30-day trial; a purchased unlock code is used in production. See `guide.md` for the exact code in Lazarus Pascal.

## Members common to every Chilkat class

Documented once per language in `common-members.md`; listed here so this page is self-contained.

| Property | Signature | Access | Meaning |
|---|---|---|---|
| `DebugLogFilePath` | `property DebugLogFilePath: string read GetDebugLogFilePath write SetDebugLogFilePath;` | read/write | If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. |
| `LastErrorHtml` | `property LastErrorHtml: string read GetLastErrorHtml;` | read-only | Provides HTML-formatted information about the last called method or property. |
| `LastErrorText` | `property LastErrorText: string read GetLastErrorText;` | read-only | Provides plain text information about the last called method or property. |
| `LastErrorXml` | `property LastErrorXml: string read GetLastErrorXml;` | read-only | Provides XML-formatted information about the last called method or property. |
| `LastMethodSuccess` | `property LastMethodSuccess: Boolean read GetLastMethodSuccess write SetLastMethodSuccess;` | read/write | Indicates the success or failure of the most recent method call: `True` means success, `False` means failure. |
| `VerboseLogging` | `property VerboseLogging: Boolean read GetVerboseLogging write SetVerboseLogging;` | read/write | If set to `True`, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. |
| `Version` | `property Version: string read GetVersion;` | read-only | Version of the component/library, such as "10.1.0" |

## Member index

| Member | Kind | Signature |
|---|---|---|
| `TimeoutSeconds` | property, read/write | `property TimeoutSeconds: Integer read GetTimeoutSeconds write SetTimeoutSeconds;` |
| `CallFunction` | method | `// funcJson is a TJsonObject object. // resultJson is a TJsonObject object. function CallFunction(funcJson: TChilkatBase;     resultJson: TChilkatBase): Boolean;` |
| `ConsoleOutputSb` | method | `// sb is a TStringBuilder object. procedure ConsoleOutputSb(sb: TChilkatBase);` |
| `Eval` | method | `// jscript is a TStringBuilder object. // resultJson is a TJsonObject object. function Eval(jscript: TChilkatBase;     resultJson: TChilkatBase): Boolean;` |
| `SetCkPermission` | method | `function SetCkPermission(const chilkatClassName: string;     const permission: string): Boolean;` |

## Properties

### Js.TimeoutSeconds

`Chilkat 11.7.0 · pascal · Js · TimeoutSeconds · property · read/write · since 11.4.0`

```pascal
property TimeoutSeconds: Integer read GetTimeoutSeconds write SetTimeoutSeconds;
```

Specify a timeout in seconds to prevent JavaScript from running indefinitely, such as in an infinite loop. By default, the value is 0, meaning no timeout is set and infinite loops will continue forever.

## Methods

### Js.CallFunction

`Chilkat 11.7.0 · pascal · Js · CallFunction · method · since 11.4.0`

```pascal
// funcJson is a TJsonObject object.

// resultJson is a TJsonObject object.

function  CallFunction(funcJson: TChilkatBase;
    resultJson: TChilkatBase): Boolean;
```

Calls a JavaScript function. The function name and arguments are passed in `funcJson`. The result is returned in `resultJson`.

Returns True for success, False for failure.

### Js.ConsoleOutputSb

`Chilkat 11.7.0 · pascal · Js · ConsoleOutputSb · method · since 11.4.0`

```pascal
// sb is a TStringBuilder object.

procedure ConsoleOutputSb(sb: TChilkatBase);
```

Returns the console output in `sb` from the last call to `Eval` .

### Js.Eval

`Chilkat 11.7.0 · pascal · Js · Eval · method · since 11.4.0`

```pascal
// jscript is a TStringBuilder object.

// resultJson is a TJsonObject object.

function  Eval(jscript: TChilkatBase;
    resultJson: TChilkatBase): Boolean;
```

Run `jscript` as a script. Return output and errors in `resultJson`.

Returns True for success, False for failure.

### Js.SetCkPermission

`Chilkat 11.7.0 · pascal · Js · SetCkPermission · method · since 11.4.0`

```pascal
function  SetCkPermission(const chilkatClassName: string;
    const permission: string): Boolean;
```

Sets sandbox related permissions for Chilkat objects. The `chilkatClassName` is the name of the Chilkat class (case-insensitive), such as `Http`, `Rest`, `"MailMan"`, `"Ftp2"`, `"Ssh"`, etc. The `chilkatClassName` can also be set to `"all"` to apply the permission to all Chilkat classes.

Possible values for `permission` are:

- `disable` - Your JavaScript code is not allowed to create an instance of the Chilkat class. A JavaScript exception is thrown when trying to create a Chilkat object of a class that is disabled.
- `sandbox` - Objects for the Chilkat class can be instantiated in JavaScript, but they have no read or write access to the local filesystem.
- `readOnly` - Objects for the Chilkat class can be instantiated in JavaScript and have read-only access to the local filesystem.
- `writeOnly` - Objects for the Chilkat class can be instantiated in JavaScript and have write-only access to the local filesystem.
- `readWrite` - Objects for the Chilkat class can be instantiated in JavaScript and have read/write access to the local filesystem.

By default, all Chilkat classes are **disabled**. Your application must enable `"all"` or specific Chilkat classes before calling `Eval` or `CallFunction` .

Returns True for success, False for failure.

## Events and callbacks

This binding has no event callbacks.

## Related classes

[`JsonObject`](https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/classes/JsonObject.md), [`StringBuilder`](https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/classes/StringBuilder.md)