# ofClass

Takes the name of a valid javascript class in form of string (*for example: 'String', 'Date', 'BigInt', etc*) then returns a new function reporting whether the received value is an instance of that class.

**ofClass** is the backbone of all the type validators:

{% code title="isString.js" %}

```javascript
import ofClass from './ofClass';

/**
 * Evaluates whether the given value is of type string
 * @param value
 * @returns {boolean}
 */
const isString = ofClass('String');

export default isString;
```

{% endcode %}

{% hint style="success" %}
**ofClass** rely on `Object.prototype.toString` to check on the received value type in order to avoid [typeof weird behaviours ](https://stackoverflow.com/questions/18808226/why-is-typeof-null-object)and encouraging a **runtime strict type validation**.
{% endhint %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://antonioru.gitbook.io/deep-waters/validators/ofclass.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.