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# generate-function
Module that helps you write generated functions in Node
```
npm install generate-function
```
[](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
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