ToFromFunctions.js

function test() { return 'Hello, World!' }

function fromFunc(func) { return func.toString() }

function toFunc(funcString) { return new Function(`return ${funcString.toString()}`)() }

let tmp = fromFunc(test)
// tmp = "function test() { console.log('Hello, World!') }"

tmp = toFunc(tmp)

tmp()
// Hello, World!

function _alert(m) { alert(m) }
toFunc(fromFunc(_alert))('Hello, World!')