---
metadata:
  - name: generator
    content: Diplodoc Platform v5.39.1
alternate:
  - https://yandex.com.tr/dev/jsapi-v2-1/doc/en/v2-1/ref/reference/modules.isDefined.md
  - https://yandex.com.tr/dev/jsapi-v2-1/doc/ru/v2-1/ref/reference/modules.isDefined.md
---
> **Documentation Index:** Fetch the complete configuration index at https://yandex.com.tr/dev/jsapi-v2-1/doc/en/llms.txt

# modules.isDefined

Static function.

Checking the module's availability by name.

**Returns** true if the module is defined, false if not.

```javascript
{ Boolean } modules.isDefined(module)
```

**Parameters:**

#|
|| **Parameter** | **Default value** | **Description**  ||
|| [`module`](#param-module)[*](*star) | — | Type: String

Module ||
|#

\* Mandatory parameter/option.

**Example:**

```javascript
if (ymaps.modules.isDefined('plugin.CustomModule')) {
    ymaps.modules.require(['plugin.CustomModule'])
        .spread(
            function (CustomModule) {
                // ...
            }
        );
}
```

[*star]: Mandatory parameter/option.