Comment by lioeters | Hacker News Reader

Comment by lioeters | Hacker News Reader

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I haven't tried it and surely not recommended, but I think it's possible to block execution with a while loop until the promise is resolved/rejected. This will be like a "synchronous await", which defeats the purpose of having async functions.

  function syncFn() {

    let result
    let state = 'pending'

    asyncFn()
      .then(data => {
        result = data
        state = 'fulfilled'
      })
      .catch(error => {
        result = error
        state = 'rejected'
      })

    while(state==='pending') {} // Stop the world

    return result
  }

  console.log('Result', syncFn())

I don't think this will work in JavaScript because that while loop will block the event loop and prevents callback from executing. For example, the following code will be blocked when running in Node.js:

    function delayedValue(val, ms) {
        return new Promise(resolve => setTimeout(() => resolve(val), ms))
    }
    
    function syncFn() {
        let result
        let state = 'pending'
    
        delayedValue(1234, 500)
            .then(data => {
                result = data
                state = 'fulfilled'
            })
            .catch(error => {
                result = error
                state = 'rejected'
            })
        while (state == 'pending') {}
        return result
    }
    console.log('before')
    console.log(syncFn())
    console.log('after')

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