# In Node.js, how do I "include" functions from my other files?

In Node.js, you can include (import) functions from other files using the `require` statement. Here's an example of how to include functions from another file:

Suppose you have a file named `mathFunctions.js` with some functions:

```jsx
// mathFunctions.js

function add(a, b) {
  return a + b;
}

function subtract(a, b) {
  return a - b;
}

module.exports = {
  add,
  subtract
};
```

Now, in another file (let's call it `app.js`), you can include and use these functions:

```jsx
// app.js

// Include (require) the mathFunctions module
const mathFunctions = require('./mathFunctions');

// Use the functions from mathFunctions module
const resultAdd = mathFunctions.add(5, 3);
const resultSubtract = mathFunctions.subtract(8, 3);

// Log the results
console.log('Addition:', resultAdd);
console.log('Subtraction:', resultSubtract);
```

In the example above:

- `require('./mathFunctions')` is used to import the module defined in `mathFunctions.js`. The `./` indicates that the module is in the same directory.
- The imported module is assigned to the variable `mathFunctions`.
- You can then use the functions from `mathFunctions` as if they were defined in the current file.

When you run `app.js`, it will output:

```
Addition: 8
Subtraction: 5
```

Remember to replace the file paths with the correct paths in your actual project. The `module.exports` statement in `mathFunctions.js` is used to export the functions from that file, making them accessible in other files that require it.

Note: With the introduction of ECMAScript modules (ESM) in newer versions of Node.js (v13.2.0 and later), you can also use `import` and `export` syntax. However, the CommonJS `require` and `module.exports` syntax is still widely used in many Node.js projects.