JavaScript implements simple barrage effect example analysis-JS Tutorial-php.cn

JavaScript implements simple barrage effect example analysis

黄舟

Release： 2017-05-27 10:26:59

Original

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This article mainly helps you to simply realize the JavaScriptbarrage effect

I don’t know if you have felt it, but the barrage is another good show! !
However, I personally prefer not to be disturbed by barrages when watching TV. Today we will write a simple barrage. How simple is it? Take a look at the effect:

As you can see from the picture, our silly HTML structure is indeed very simple.
is composed of a p, an input box and a button.

 <p id="box" class="box"></p>
 <input type="text" id="txt" />
 <button onclick="send()">提交内容</button>

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First post jsCode:

 function $(str) {
  return document.getElementById(str);
 }
 function send() {
  var word = $(&#39;txt&#39;).value;
  var span = document.createElement(&#39;span&#39;);
  var top = parseInt(Math.random() * 500) - 20;
  var color1 = parseInt(Math.random() * 256);
  var color2 = parseInt(Math.random() * 256);
  var color3 = parseInt(Math.random() * 256);
  var color = "rgb(" + color1 + "," + color2 + "," + color3 + ")";
  top = top < 0 ? 0 : top;
  span.style.position = &#39;absolute&#39;;
  span.style.top = top + "px";
  span.style.color = color;
  span.style.left = &#39;500px&#39;;
  span.style.whiteSpace = &#39;nowrap&#39;;
  var nub = (Math.random() * 10) + 1;
  span.setAttribute(&#39;speed&#39;, nub);
  span.speed = nub;
  span.innerHTML = word;
  $(&#39;box&#39;).appendChild(span);
  $(&#39;txt&#39;).value = "";
 }
 setInterval(move, 200);
 function move() {
  var spanArray = $(&#39;box&#39;).children;
  for (var i = 0; i < spanArray.length; i++) {
   spanArray[i].style.left =
    parseInt(spanArray[i].style.left) - spanArray[i].speed + &#39;px&#39;;
  }
 }

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The principle is briefly explained:

First step, We need to get the content in the input box, var word = $('txt').value;
Second step, we have to try our best to stuff this content into the p to be scrolled and displayed Inside, there are three principles: ① Random color ② Random height ③ The distance from the left border changes in real time;
The third step, append this content to p $('box').appendChild (span);

It can be seen from the principles of the above steps that the second step is the most critical step,

realize the first principle:

 var color1 = parseInt(Math.random() * 256);
 var color2 = parseInt(Math.random() * 256);
 var color3 = parseInt(Math.random() * 256);
 var color = "rgb(" + color1 + "," + color2 + "," + color3 + ")";
 span.style.color = color;

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小Extension:

RGB(R,G,B);
R:
Red value. Positive Integer | Percentage
G:
Green value. Positive integer | Percentage
B:
Blue value. Positive integer | Percent
This should be easy to understand.

Implement the second principle:

var top = parseInt(Math.random() * 500) - 20;
top = top < 0 ? 0 : top;
span.style.top = top + "px";

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Implement the third principle:

 span.style.left = &#39;500px&#39;;
 setInterval(move, 200);
 function move() {
  var spanArray = $(&#39;box&#39;).children;
  for (var i = 0; i < spanArray.length; i++) {
   spanArray[i].style.left =
    parseInt(spanArray[i].style.left) - spanArray[i].speed + &#39;px&#39;;
  }
 }

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is to use the principle of timer to let the value of left changes in real time.

At this point, it should be very clear.

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