如何使用JavaScript移动多个DOM元素？

Question

我创建了一个名为Circle的对象，并有两个该对象的实例，分别叫做circle1和circle2。我试图让它们交换位置，但目前只有其中一个在移动。

Javascript：

var gap = 6, size= 60;
var Circle = function(t,l, color){
        var elem = document.createElement('div');
        t = t,
        l = l;

        elem.setAttribute("class", "circle");
        elem.style.backgroundColor = color;

        // init positions
        elem.style.top  = gap+t*(size+2*gap) + "px";
        elem.style.left = gap+l*(size+2*gap) + "px";
        document.body.appendChild(elem);

        this.getPosition = function(){
            return [t,l];
        };

        this.setPosition = function(arr){
            t = arr[0];
            l = arr[1];
            elem.style.top  = gap+t*(size+2*gap) + "px";
            elem.style.left = gap+l*(size+2*gap) + "px";
        };
}

// make two new circle objects 
var circle1 = new Circle(0, 0, "blue");
var circle2 = new Circle(0, 1, "red");

// we need the circles to swap positions
setTimeout(function(){
    circle1.setPosition(circle2.getPosition());
    circle2.setPosition(circle1.getPosition()); // this is not working
}, 1000);

我已经将此代码放在jsFiddle上，以使它更容易使用：http://jsfiddle.net/rhL7671p/

- Unknown

---

当你在下一行调用getPosition()时，circle1的位置已经发生了改变。 - Jamiec

Answer 1

只需缓存第一个圆的位置：

setTimeout(function(){
   var pos = circle1.getPosition();
   circle1.setPosition( circle2.getPosition() );
   circle2.setPosition( pos );
}, 1000);

示例 Fiddle

在这行代码之后：

circle1.setPosition(circle2.getPosition());

第一个圆的位置被第二个圆的位置覆盖。因此下一行代码没有效果。在JavaScript中不存在并行执行代码的情况，因为只有一个线程（有一些例外...）。

为了解决这个问题：先获取一个（或两个）位置，然后在之后设置它们。

- Sirko

Answer 2

在更新位置之前，请存储左圆的位置。

setTimeout(function(){
    var c = circle1.getPosition();
    circle1.setPosition(circle2.getPosition());
    circle2.setPosition(c);
}, 1000);

var gap = 6, size= 60;
var Circle = function(t,l, color){
  var elem = document.createElement('div');
        t = t,
        l = l;
    
        elem.setAttribute("class", "circle");
        elem.style.backgroundColor = color;
        elem.style.top  = gap+t*(size+2*gap) + "px";
        elem.style.left = gap+l*(size+2*gap) + "px";
        document.body.appendChild(elem);

        this.getPosition = function(){
         return [t,l];
        }

        this.setPosition = function(arr){
         t = arr[0];
            l = arr[1];
         elem.style.top  = gap+t*(size+2*gap) + "px";
         elem.style.left = gap+l*(size+2*gap) + "px";
     }

        
 }

var circle1 = new Circle(0,0, "blue");
var circle2 = new Circle(0,1, "red");

// we need the circles to swap positions
setTimeout(function(){
    var c = circle1.getPosition();
    circle1.setPosition(circle2.getPosition());
    circle2.setPosition(c);
}, 1000);

console.log(circle2)

.circle{
    width:60px;
    height:60px;
    border-radius: 50px;
    background-color:red;
    position:absolute;
    -webkit-transition-property: top, left;
        -webkit-transition-duration: 0.3s;
}

- brbcoding

Answer 3

< p >在移动第一个圆之后，getPosition的结果可能不是您所期望的，因此请在移动之前将其缓存。

setTimeout(function(){
    var a = circle2.getPosition(),
        b = circle1.getPosition();
    circle1.setPosition(a);
    circle2.setPosition(b);
}, 1000);

- Paul S.

Answer 4

这是因为当您尝试获取元素的位置时，它已经具有了新值。一个可能的解决方案是使用本地变量：

var gap = 6,
  size = 60;
var Circle = function(t, l, color) {
  var elem = document.createElement('div');
  t = t,
    l = l;

  elem.setAttribute("class", "circle");
  elem.style.backgroundColor = color;
  elem.style.top = gap + t * (size + 2 * gap) + "px";
  elem.style.left = gap + l * (size + 2 * gap) + "px";
  document.body.appendChild(elem);

  this.getPosition = function() {
    return [t, l];
  }

  this.setPosition = function(arr) {
    t = arr[0];
    l = arr[1];
    elem.style.top = gap + t * (size + 2 * gap) + "px";
    elem.style.left = gap + l * (size + 2 * gap) + "px";
  }


}

var circle1 = new Circle(0, 0, "blue");
var circle2 = new Circle(0, 1, "red");

// we need the circles to swap positions
setTimeout(function() {
  //use local variables to keep circles position
  var circle1Pos = circle1.getPosition();
  var circle2Pos = circle2.getPosition()
  circle1.setPosition(circle2Pos);
  circle2.setPosition(circle1Pos);
}, 200);

.circle {
  width: 60px;
  height: 60px;
  border-radius: 50px;
  background-color: red;
  position: absolute;
  -webkit-transition-property: top, left;
  -webkit-transition-duration: 0.3s;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

- Alex Char