Question

<!DOCTYPE>
<html>
<body>
<img id="traffic" src="assets/red.gif">
<on type="on" onclick="ChangeLights()">Change Lights</on>
<script>
var lights = [
"assets/red.gif",
"assets/yellow.gif",
"assets/green.gif",
"assets/yellow.gif",
];
var index = 0;
function ChangeLights() {
  setInterval(function () {ChangeLights();}, 1000);
  
index = index + 1;
if (index == lights.length) index = 0;
var image = document.getElementById('traffic');
    image.src=lights[index];
}
</script>
</body>
</html>

嗨,我正在尝试使用 JavaScript 制作动画脚本,以便一旦按下按钮,交通灯序列在计时器上从红色--绿色-变化。我只希望序列循环一次。但是,当我将 setInterval 函数实现到函数中时,灯光仅从红色--绿色-红色变化。谢谢任何帮助!

1

0

Answer 1

var lights = {
  red: "https://upload.wikimedia.org//commons/thumb/4/45/Traffic_lights_red.svg/200px-Traffic_lights_red.svg.png",
  yellow: "https://upload.wikimedia.org//commons/thumb/1/19/Traffic_lights_yellow.svg/200px-Traffic_lights_yellow.svg.png",
  green: "https://upload.wikimedia.org//commons/thumb/b/b2/Traffic_lights_dark_green.svg/200px-Traffic_lights_dark_green.svg.png"
};
var sequence = ['red', 'yellow', 'green', 'yellow'];
function startChangeLights() {
  for (var index = 0; index < sequence.length; index++) {
    changeLight(index, sequence[index]);
  }
  function changeLight(index, color) {
    setTimeout(function() {
      var image = document.getElementById('traffic');
      image.src = lights[color];
    }, index * 1000);
  }
}

<div>
  <img height=100px id="traffic" src="https://upload.wikimedia.org//commons/thumb/4/45/Traffic_lights_red.svg/200px-Traffic_lights_red.svg.png">
</div>
<div>
  <on type="on" onclick="startChangeLights()">Change Lights</on>
</div>

https://codepen.io/anon/pen/VbKQNj?editors=1011

Answer 2

如果你正在寻找一个时间序列，你必须在 javascript 中使用“setTimeout”方法，此外，定义一个内部函数，如下所示：

var lights = [
"assets/red.gif",
"assets/yellow.gif",
"assets/green.gif",
"assets/yellow.gif",
];
var index = 0;
function ChangeLights() {
  
  function innerChangeLight(){
index = index + 1;
if (index == lights.length) index = 0;
var image = document.getElementById('traffic');
    image.src=lights[index];
  }
  innerChangeLight();
  setTimeout(function () {
      innerChangeLight();
    }, 1000);
  
}

<!DOCTYPE>
<html>
<body>
<img id="traffic" src="assets/red.gif">
<on type="on" onclick="ChangeLights()">Change Lights</on>
</body>
</html>

Answer 3

试试这个：

var lights = [
"assets/red.gif",
"assets/yellow.gif",
"assets/green.gif",
"assets/yellow.gif",
];
var index = 0;
function ChangeLights(){
  setInterval(function() {
    
    if(index == lights.length) {
      return;
    }
    var image = document.getElementById('traffic');
    image.src=lights[index];
    index = index + 1;
  }, 1000);
  
}

<img id="traffic" src="assets/red.gif"><br>
<on onclick="ChangeLights()">Change Lights</on>

Answer 4

“交通灯”的新实例：

交通灯不能总是在每个灯的持续时间相同。

所以，我开始扩展这个 html 代码。改进的代码在每个灯中都有不同的秒数：

// Traffic Light
// Improved with different durations in every light!
// But in this html code, i will use input tag instead
var TrafficLights = (function() {
  // The image   
  var imageTag = document.getElementById("lightImg");
  // Keep track of whether the sequence is running    
  var running = false;
  // Different stages of the traffic light (Also defines the light)    
  var stages = [
    {
      "name": "red",
      "path": "https://upload.wikimedia.org//commons/thumb/4/45/Traffic_lights_red.svg/200px-Traffic_lights_red.svg.png",
    },
    {
      "name": "green",
      "path": "https://upload.wikimedia.org//commons/thumb/b/b2/Traffic_lights_dark_green.svg/200px-Traffic_lights_dark_green.svg.png"
    },
    {
      "name": "yellow",
      "path": "https://upload.wikimedia.org//commons/thumb/1/19/Traffic_lights_yellow.svg/200px-Traffic_lights_yellow.svg.png"
    }
  ];
  // Different amount of seconds in every light change (Must be an positive integer!)
  var seconds_every_step = [
    18,
    24,
    3
  ];
  // Current stage of the traffic light 
  var stage = 0;
  // Current steps of the traffic light   
  var steps = 0;
  // Timer for automatically changing light    
  var timer = null;
  /**     * Start the traffic light sequence     *     */
  function start() {
    // Mark that the light sequence is running        
    running = true;
    // Tell the light to change        
    changeLight();
  }
  /**     * Stop the sequence from running     *     */
  function stop() {
    // Mark that the sequence is not running        
    running = false;
    // Stop the automatic timer from running        
    clearInterval(timer);
  }
  /**     * Change the light to the next one in the sequence     *     */
  function changeLight() {
    // If the timer is not running, this function does not need to do anything        
    if (running === false) {
      clearInterval(timer);
      return;
    } else {};
    // If the current stage gets higher than the number of stages there are, reset to 0        
    if (stage >= stages.length) {
      stage = 0;
    } else {};
    // If the current steps gets higher than the number of seconds in a step there are, reset to 0    
    if (steps >= seconds_every_step.length) {
      steps = 0;
    } else {};
    // Get the image from the list of stages        
    var image = stages[stage];
    var wait_seconds = seconds_every_step[steps];
    // Update the image tag and defines the light name
    imageTag.src = image.path;
    imageTag.alt = String("Traffic light color is " + image.name + ".");
    // Increase the current stage by 1        
    stage++;
    // Increase the current steps by 1        
    steps++;
    // Set a timeout to change the light at the next interval        
    timer = setTimeout(changeLight, wait_seconds * 1000);
  }
  // These functions will be available on the `TrafficLights` object to allow interaction    
  return {
    start: start,
    stop: stop
  }
})();

<input type="image" width="20px" id="lightImg" src="" alt="">
<br/>
<p>
  <on type="on" onclick="TrafficLights.start()">Start Sequence</on> <on type="on" onclick="TrafficLights.stop()">Stop Sequence</on>
</p>