ts-simple-ast/docs/manipulation/index.md

TypeScript compiler wrapper for AST navigation and code generation.

---
title: Manipulating the AST
---

## Manipulating the AST

Most information about manipulation can be found in the [Details](../details) section. This section only contains general information about manipulation.

### Replacing any node with new text

This can be achieved with the `.replaceWithText(...)` method that exists on any node.

#### Example

Given the following code:

```typescript
let myVariable = Some.Property.Access.Expression;
```

You can replace the property access expression with new text by doing the following:

```typescript
const originalInitializer = sourceFile.getVariableDeclarations()[0].getInitializerOrThrow();
const newInitializer = originalInitializer.replaceWithText("MyReference");
```

That will make the source file hold the following text:

```typescript
let myVariable = MyReference;
```

Note that `originalInitializer` will be disposed after calling `.replaceWithText(...)` on it—an error will be thrown if you try to use it.
You will have to use the new node returned by that method.

### Inserting, replacing, and removing text

In some scenarios, a simple to use API might not have been implemented. If you find that's the case, open an issue on GitHub.

In the meantime, you can insert, replace, and remove text using the following methods, but *generally you will want to avoid using these if possible*:

```typescript
// insert text
sourceFile.insertText(0, "// some comment\n");
// replace text
sourceFile.replaceText([3, 7], "a"); // "// a comment\n"
// remove text
sourceFile.removeText([sourceFile.getPos(), sourceFile.getEnd()]);
```

These methods are also available on any node that has a body (functions, classes, enums, etc.)

#### **Warning**

If you use `insertText`, `replaceText`, or `removeText`, all previously navigated descendants of the node will be disposed and not be available for use—an error will be thrown
if you try to use them. You will have to renavigate to those nodes.

For example:

```typescript
let classDeclaration = sourceFile.addClass({ name: "MyClass" });
sourceFile.insertText(0, "// some comment\n");

// this will throw...
classDeclaration.getInstanceProperties();

// you'll need to get the reference again:
classDeclaration = sourceFile.getClass("MyClass")!;
```