# generate-function

> Module that helps you write generated functions in Node

Latest version **2.3.1** (published 2018-08-31) · MIT license · 0 weekly downloads

## Install

```sh
npm install generate-function
pnpm add generate-function
yarn add generate-function
bun add generate-function
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 2.3.1 |
| Published | 2018-08-31 |
| First published | 2014-07-30 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 1 |
| Unpacked size | 8.8 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 78 |
| Author | Mathias Buus |
| Maintainers | mafintosh |
| Keywords | generate, code, generation, function, performance |

## Links

- npm: https://www.npmjs.com/package/generate-function
- Repository: https://github.com/mafintosh/generate-function
- Issues: https://github.com/mafintosh/generate-function/issues
- npm.io page: https://npm.io/package/generate-function

## Dependencies (1)

- [is-property](https://npm.io/package/is-property.md) ^1.0.2

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## Recent versions

- 2.3.1 (latest) — 2018-08-31
- 2.3.0 — 2018-08-31
- 2.2.1 — 2018-08-31
- 2.2.0 — 2018-08-27
- 2.0.0 — 2014-08-21
- 1.1.0 — 2014-08-01
- 1.0.3 — 2014-08-01
- 1.0.2 — 2014-07-30
- 1.0.1 — 2014-07-30
- 1.0.0 — 2014-07-30
- 0.0.0 — 2014-07-30

## README

# generate-function

Module that helps you write generated functions in Node

```
npm install generate-function
```

[![build status](http://img.shields.io/travis/mafintosh/generate-function.svg?style=flat)](http://travis-ci.org/mafintosh/generate-function)

## Disclamer

Writing code that generates code is hard.
You should only use this if you really, really, really need this for performance reasons (like schema validators / parsers etc).

## Usage

``` js
const genfun = require('generate-function')
const { d } = genfun.formats

function addNumber (val) {
  const gen = genfun()

  gen(`
    function add (n) {')
      return n + ${d(val)}) // supports format strings to insert values
    }
  `)

  return gen.toFunction() // will compile the function
}

const add2 = addNumber(2)

console.log('1 + 2 =', add2(1))
console.log(add2.toString()) // prints the generated function
```

If you need to close over variables in your generated function pass them to `toFunction(scope)`

``` js
function multiply (a, b) {
  return a * b
}

function addAndMultiplyNumber (val) {
  const gen = genfun()
  
  gen(`
    function (n) {
      if (typeof n !== 'number') {
        throw new Error('argument should be a number')
      }
      const result = multiply(${d(val)}, n + ${d(val)})
      return result
    }
  `)

  // use gen.toString() if you want to see the generated source

  return gen.toFunction({multiply})
}

const addAndMultiply2 = addAndMultiplyNumber(2)

console.log(addAndMultiply2.toString())
console.log('(3 + 2) * 2 =', addAndMultiply2(3))
```

You can call `gen(src)` as many times as you want to append more source code to the function.

## Variables

If you need a unique safe identifier for the scope of the generated function call `str = gen.sym('friendlyName')`.
These are safe to use for variable names etc.

## Object properties

If you need to access an object property use the `str = gen.property('objectName', 'propertyName')`.

This returns `'objectName.propertyName'` if `propertyName` is safe to use as a variable. Otherwise
it returns `objectName[propertyNameAsString]`.

If you only pass `gen.property('propertyName')` it will only return the `propertyName` part safely

## License

MIT

---
_Source: https://npm.io/package/generate-function · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._