How to use callback asynchronously

Question

console.log("before")

function g(p,callback){
    callback('1')
}

g(1,(re)=>{
    console.log(re);
})

console.log("after")

The result is before 1 after. How to make the function call async means the result should be before after 1 without setTimeout function

The usecase is like

I have one api call inside a function and sending response after the this function call.But because this function is called synchronously sending response is delayed.So i want to send response before api call

console.log("before callback")

apiRes.url = [url];
apimanager.callfunc(requestBody, apiRes,(err,success)=>{
    console.log("success ",success)
    console.log("inside callback");
});

console.log("after callback")

return response.json(someresponse)

Answer 1

You could use Promise.resolve():

console.log("before")

function g(p, callback) {
  callback('1')
}

g(1, (re) => {
  Promise.resolve().then(() => {
    console.log(re);
  });
})

console.log("after")