Issues to note when using css3 animation and jquery animation_html/css_WEB-ITnose

When I was writing a demo a while ago, I encountered a problem. When adding css3 or jquery animation to an element, the css attribute of the element cannot be accurately obtained before the animation ends.

1. css3 animation discussion

Look at the code first:

html:

<div id="hehe"></div><button class="change">change</button><button class="get">get</button>

css:

#hehe {    width: 100px;    height: 100px;    padding: 10px;    background: red;    -webkit-transition: all 10s ease-out;    -moz-transition: all 10s ease-out;    -o-transition: all 10s ease-out;    transition: all 10s ease-out;}

js:

$(document).ready(function() {    $('.change').click(function() {        $('#hehe').width(400);    });    $('.get').click(function() {        console.log($('#hehe').width());    });});

The code is very simple. We added a red background color to the hehe div, and used the animation smoothing effect css3 trasition in css3 (for how to use css3 trasition, please refer to this article: http://www.w3cplus.com/content/css3-transition , written in great detail). That is to say, when hehe changes CSS attributes such as width, height, background or font, there will be an ease-out (slow down) smooth transition effect, which lasts for 10 seconds. For example, if we click the change button, the width of hehe will take 10 seconds and slowly increase to 400px, producing an animation effect.

Here comes the question: When the animation is in progress, I click the get button, what is the width of the hehe output by the console?

At first I thought it was 400, because when I clicked change, I saw "ce6fcc1366b86049ecea2ac33716a13d16b28748ea4df4d9c2150843fecfba68" when inspecting the element. The answer is no, what we get is the width of hehe at the click moment during the animation.

Let’s modify the console code:

console.log($('#hehe').css('width');

Now we see that during the entire animation process, when we click get, all we get is 400px. This shows that width() in jquery obtains the width of the element in real time, while css('width') simply obtains the css value of the element, because it also has units.

2. jquery animation discussion

jquery animation is easier to understand. We remove the css code of css3 transition and replace it with jquery animate.

$(document).ready(function() {    console.log($('#hehe').width());    $('.change').click(function() {        $('#hehe').animate({width: "400px"}, 10000);    });    $('.get').click(function() {        console.log($('#hehe').width());    });});

Since jquery animation actually dynamically adds styles to elements, whether we use width() or css('width' ) to obtain the width of hehe, which changes dynamically. However, there is one difference. The width obtained by using width has no unit px, and they are all integers; but the width obtained by using css('width') has units, and the number of digits after the decimal point is very long.

Summary:

After discussing so much, the key is to tell everyone that when using animation, if you go to get it immediately Changing css attributes, especially width and height, are prone to problems. You must wait until the animation ends to get the attributes of these elements. Or you can specify the CSS properties you want to animate. For example, if you want to get the width and height in animation, but in fact the animation effect you want is just a change in background color, then you can write like this when writing css3 transition

-webkit-transition: background .7s ease-out;-moz-transition: background .7s ease-out;-o-transition: background .7s ease-out;transition: background .7s ease-out;

In this way, the animation effect will only be displayed on the background color, and the width and height will not change dynamically.

Similarly, for the other two effects in css3 animation, transform (http://www.w3cplus.com/content/css3-transform) and animation (http://www.w3cplus.com/content /css3-animation) also did a test and found that it is the same as transition. During the animation process, the element attributes change dynamically. Even when animation is used, the width obtained by using css('width') also changes. . Interested students can try it.

Therefore, we need to pay more attention to the impact of animation when using css3 animation.