JavaScript implements simple barrage effect example analysis
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>
First post jsCode:
function $(str) {
return document.getElementById(str);
}
function send() {
var word = $('txt').value;
var span = document.createElement('span');
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 = 'absolute';
span.style.top = top + "px";
span.style.color = color;
span.style.left = '500px';
span.style.whiteSpace = 'nowrap';
var nub = (Math.random() * 10) + 1;
span.setAttribute('speed', nub);
span.speed = nub;
span.innerHTML = word;
$('box').appendChild(span);
$('txt').value = "";
}
setInterval(move, 200);
function move() {
var spanArray = $('box').children;
for (var i = 0; i < spanArray.length; i++) {
spanArray[i].style.left =
parseInt(spanArray[i].style.left) - spanArray[i].speed + 'px';
}
}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;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";
Implement the third principle:
span.style.left = '500px';
setInterval(move, 200);
function move() {
var spanArray = $('box').children;
for (var i = 0; i < spanArray.length; i++) {
spanArray[i].style.left =
parseInt(spanArray[i].style.left) - spanArray[i].speed + 'px';
}
}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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