使用 css transition 和 vanilla JavaScript 更改不透明度仅在淡出时有效

Question

这个代码笔显示了我的问题：http ://codepen.io/PiotrBerebecki/pen/pNvpdG

当用户点击大按钮时，cssopacity减少到 0。因为我应用了以下规则：transition: opacity 0.5s ease-in-out;淡出动画是平滑的。

我想在下一个按钮淡入时实现相同的平滑过渡。但是由于某种原因，下一个按钮突然出现而没有任何过渡。

你知道是什么导致了这个问题以及如何解决它吗？

console.clear();

(function() {
  
  // Data for the app
  const model = {
    buttons: ['tomato', 'blue'],
    currentButton: -1
  };
  
  // Logic for the app
  const controller = {
    init: function() {
      view.init();
    },
    getButtonName: function() {
      model.currentButton = (model.currentButton + 1) % model.buttons.length;
      return model.buttons[model.currentButton];
    }
  };
  
  // View for the app
  const view = {
    init: function() {
      this.root = document.getElementById('root');
      this.showNext();
    },
    
    animationDelay: 500,
    
    showNext: function() {
      // Get next button name
      const buttonName = controller.getButtonName();
      
      // Create button DOM element
      const buttonElement = document.createElement('div');
      buttonElement.className = 'button';
      buttonElement.id = buttonName;
      buttonElement.textContent = buttonName;
      buttonElement.style.opacity = 0;
      
      // Add event listender for the button
      buttonElement.addEventListener('click', event => {
        // Reduce opacity
        buttonElement.style.opacity = 0;
        // Remove the button from DOM
        setTimeout(() => {
          this.root.removeChild(buttonElement);
        }, this.animationDelay + 10);
        // Start the function to show next button
        setTimeout(() => {
          this.showNext();
        }, this.animationDelay + 20);
      });
      
      // Add button to DOM
      this.root.appendChild(buttonElement);
      
      // Show button by increasing opacity
      buttonElement.style.opacity = 1;
      
    }
  };
  
  // Start the app
  controller.init();

}());

#tomato {
  background: tomato;
}

#blue {
  background: DeepSkyBlue;
}

.button {
  transition: opacity 0.5s ease-in-out;
  width: 100%;
  height: 50vh;
  border: solid 3px black;
  cursor: pointer;
}

<div id="root"></div>

Answer 1

这应该有效，代码笔链接：http://codepen.io/saa93/pen/gLbvmQ

您需要添加它而不是直接将不透明度设置为 1

// Show button by increasing opacity
buttonElement.style.opacity = 0;
setTimeout(() => {
    buttonElement.style.opacity = 1;
}, this.animationDelay + 20);