JAVASCRIPT. How to make several functions execute asynchronously BY USING CALLBACK

[muf]

https://stackoverflow.com/questions/2190850/create-a-custom-callback-in-javascript

[muf]

function snycronizationControl(list){
    if(list.length <= 1){
        callback()
    }
    else{
        snycronizationControl(list.splice(0,1))
    }
}
undefined
function a(){
    console.log("A")
}
undefined
function b(){
    console.log("B")
}
undefined
function C(){
    console.log("C")
}

Trying for the test ...