Recursive async function in JavaScript

Question

I'm trying to write a recursive function using async/await in JavaScript. This is my code:

async function recursion(value) {
  return new Promise((fulfil, reject) => {
    setTimeout(()=> {
      if(value == 1) {
        fulfil(1)
      } else {
        let rec_value = await recursion(value-1)
        fulfil(value + rec_value)
      }
    }, 1000)
    })
}

console.log(await recursion(3))

But I have syntax error:

let rec_value = await recursion(value-1)
                              ^^^^^^^^^

SyntaxError: Unexpected identifier

user_6152308 · Answer

let rec_value = await recursion(value-1)

You can only await within an async function thus the JS engine is unable to parse the code.

Instead modify the usage to below since a async function always returns a Promise.

recursion(value-1).then((value) => { console.log(value)})

Refer to detailed documentation here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function

Recursive async function in JavaScript

3 Answers