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# FunctionExpression class
This class defines the base class for Firestore [Pipeline](./firestore_pipelines.pipeline.md#pipeline_class) functions, which can be evaluated within pipeline execution.

Typically, you would not use this class or its children directly. Use either the functions like [and()](./firestore_pipelines.md#and_e0c48bd)<!-- -->, [equal()](./firestore_pipelines.md#equal_b3c3382)<!-- -->, or the methods on [Expression](./firestore_pipelines.expression.md#expression_class) ([Expression.equal()](./firestore_pipelines.expression.md#expressionequal)<!-- -->, [Expression.lessThan()](./firestore_pipelines.expression.md#expressionlessthan)<!-- -->, etc.) to construct new Function instances.

<b>Signature:</b>

```typescript
export declare class FunctionExpression extends Expression 
```
<b>Extends:</b> [Expression](./firestore_pipelines.expression.md#expression_class)

## Constructors

|  Constructor | Modifiers | Description |
|  --- | --- | --- |
|  [(constructor)(name, params)](./firestore_pipelines.functionexpression.md#functionexpressionconstructor) |  | Constructs a new instance of the <code>FunctionExpression</code> class |

## Properties

|  Property | Modifiers | Type | Description |
|  --- | --- | --- | --- |
|  [expressionType](./firestore_pipelines.functionexpression.md#functionexpressionexpressiontype) |  | [ExpressionType](./firestore_pipelines.md#expressiontype) |  |
|  [name](./firestore_pipelines.functionexpression.md#functionexpressionname) |  | string |  |
|  [params](./firestore_pipelines.functionexpression.md#functionexpressionparams) |  | [Expression](./firestore_pipelines.expression.md#expression_class)<!-- -->\[\] |  |

## FunctionExpression.(constructor)

Constructs a new instance of the `FunctionExpression` class

<b>Signature:</b>

```typescript
constructor(name: string, params: Expression[]);
```

#### Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  name | string |  |
|  params | [Expression](./firestore_pipelines.expression.md#expression_class)<!-- -->\[\] |  |

## FunctionExpression.expressionType

<b>Signature:</b>

```typescript
readonly expressionType: ExpressionType;
```

## FunctionExpression.name

<b>Signature:</b>

```typescript
readonly name: string;
```

## FunctionExpression.params

<b>Signature:</b>

```typescript
readonly params: Expression[];
```