Changing a function into a string and reversing the process in JavaScript

Question

Changing a function into a string and reversing the process in JavaScript

// Just an interesting point to note: The same outcome occurs when utilizing the full syntax as shown below.
const a = () => {
  return "hello world"
}
const stringifiedA = a.toString()
const b = new Function(stringifiedA)
console.log(b());  // undefined

Therefore, b serves as a closure of a, and there doesn't seem to be a way to prevent this wrapping. Has anyone discovered how to obtain the function without creating a closure?

javascript

Answer 1

Answer №1

New Function requires a function body as input, which is clearly explained on the mdn website:

The function definition should be a string containing JavaScript statements.

It's important to note that the parameters for the function are not included in this string and need to be passed separately.

There are multiple approaches to achieving this functionality:

You can utilize eval, but if that's not an option (as mentioned in your question), consider the alternative approach:

const a = () => {
  return "hello world"
}
const aString = a.toString()
const b = eval(aString)
console.log(b());  // "hello world"

Please be cautious: similar to using New Function, when dealing with a stringified function that isn't entirely controlled by you, there may be risks of code injection.

If you prefer to stick to using New Function, ensure you include a return statement and then execute it to unwrap the wrapper:

const a = () => {
  return "hello world"
}
const aString = a.toString()
const b = new Function("return " + aString)();
console.log(b());  // "hello world"

Answer 2

New Function requires a function body as input, which is clearly explained on the mdn website:

The function definition should be a string containing JavaScript statements.

It's important to note that the parameters for the function are not included in this string and need to be passed separately.

There are multiple approaches to achieving this functionality:

You can utilize eval, but if that's not an option (as mentioned in your question), consider the alternative approach:

const a = () => {
  return "hello world"
}
const aString = a.toString()
const b = eval(aString)
console.log(b());  // "hello world"

Please be cautious: similar to using New Function, when dealing with a stringified function that isn't entirely controlled by you, there may be risks of code injection.

If you prefer to stick to using New Function, ensure you include a return statement and then execute it to unwrap the wrapper:

const a = () => {
  return "hello world"
}
const aString = a.toString()
const b = new Function("return " + aString)();
console.log(b());  // "hello world"

Changing a function into a string and reversing the process in JavaScript

Answer №1

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