[如何运行调用函数的函数，请先完成，然后再调用下一个函数。创建一个回调函数

Question

[当用户单击任何图像时，所有图像（images_holder）都会逐渐淡出。然后在消失后，另一张图像逐渐消失，然后在3秒钟后该图像逐渐消失。之后，images_holder再次淡入。我的问题是在推子完成之前，secondStep函数已经在运行。

我要完成的第一步是先完成推子功能，然后再执行第二步。一直在尝试创建此回调，但没有运气。

这是我的html

<div id="container">
    <!--<img src="images/background.jpg"/>-->
    <div id="faces_holder">
        <img id="face1" onclick="loadUnload(1)" src="images/face_03.png" width=350; height=656;/><img id="face2" onclick="loadUnload(2)" src="images/face_04.png" width=350; height=656;/><img id="face3" onclick="loadUnload(3)" src="images/face_05.png" width=350; height=656;/><img id="face4" onclick="loadUnload(4)" src="images/face_06.png" width=350; height=656;/><img id="face5" onclick="loadUnload(5)" src="images/face_07.png" width=350; height=656;/>
    </div>
    <div id="pop_face"><img id="popface_img" src=""/></div>
</div>

这是我的JavaScript：

    var id = "";
    var kindface=0;
    var fadeIn;
    var counterValue;
    var objHolder;


    function loadUnload(kindface){
        //FADEIN FADEOUT    
        function fader() {
            if(fadeIn == true){
                counterValue++;
                //setPoint = 9;
            }else{
                counterValue--;  // update parameters
                //console.log("hit");
            }
            objHolder.style.opacity = "0."+counterValue // show frame
            if (counterValue == setPoint){  // check finish condition
                clearInterval(id);
                console.log("end fader");
            }
        }

        //FADEOUT

更新

我刚刚添加了第三步，我将如何实现它？我希望第二步在secondStep完成推子功能后运行？

function thirdstep() {
        console.log("begin second step: ")

            fadeIn = true;
            counterValue = 0;
            setPoint = 9;
            objHolder = document.getElementById("popface_img");
            objHolder.src = "images/"+ kindface +".png";

            id = setInterval(fader, 100); // draw every 100ms
            console.log("end second step: ")
        }

        function secondStep() {
            console.log("begin second step: ")

            fadeIn = true;
            counterValue = 0;
            setPoint = 9;
            objHolder = document.getElementById("popface_img");
            objHolder.src = "images/"+ kindface +".png";

            id = setInterval(fader, 100); // draw every 100ms
            console.log("end second step: ")
        }

        function firstStep(callback) {
            console.log("begin first step: ")

            fadeIn = false;
            objHolder = document.getElementById("faces_holder");
            counterValue = 10;
            setPoint = 0;


            id = setInterval(callback, 100); // draw every 100ms
            console.log("end first step: ")
            secondStep();

        }


        //RUN FIRST STEP FUNCTION 
        console.log("BEGIN process ")             
            firstStep(fader);

        console.log("END OF ALL process ")

    }

</script>

Answer 1

在您的代码中：