JS capture page scroll bar-JS Tutorial-php.cn

This time I will bring you JS to capture the page scroll bar. What are the precautions for js to capture the page scroll bar? the following is a practical case, let’s take look. <>

precautions for js to capture the page scroll bar? following is a practical case, let’s take look. <>

Preface

In the process of writing a plug-in recently, I need to use JS to determine whether there is a scroll bar. Search After a while, the general methods are similar, but they are a bit verbose and the code is not concise enough. Finally, by referring to different methods, I wrote a relatively simple method. When judging the scroll bar, you also need to calculate the width of the scroll bar. I will share it with you through this article.

Why should we judge the scroll bar

The need to judge the scroll bar is often used in pop-up window plug-ins, because most pop-up windows will add

overflow: hidden attribute. If the page is relatively long, the page will shake after adding this attribute.

In order to enhance the user experience, add themargin-left  attribute to offset the scroll bar afteroverflow: hidden
          by determining whether there is a scroll bar. location. < code>>
How to determine whether there is a scroll bar
In fact, only one line of JS is needed to test compatibility with IE7
        
         function hasScrollbar() { return document.body.scrollHeight > (window.innerHeight || document.documentElement.clientHeight); }
         
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Generally, usedocument.body.scrollHeight>window.innerHeight
          can be judged. < code>>
But in IE7 and IE8,window.innerHeight
          is < code>
          underfined
          , so in order to be compatible with IE7 and IE8, you need to usedocument.documentElement.clientHeight
           property calculates window height. < code>>
         >
The method of calculating the scroll bar width
still takes the pop-up window as an example, because the scroll bars of IE 10 and above and mobile browsers do not occupy the page width. Transparent style (IE 10 and above browsers can restore the original scroll bar style through CSS properties), so in order to further enhance the user experience, we also need to calculate the width of the scroll bar and add a reasonablemargin-left ## according to the situation. #Value.
The method to calculate the width of the scroll bar is relatively simple. Create a new p element with a scroll bar and pass the
offsetWidth and  clientwidth of the element. the difference < code> can be obtained. i will learn from method in Magnific-popup
function getScrollbarWidth() { var scrollp = document.createElement("p"); scrollp.style.cssText = 'width: 99px; height: 99px; overflow: scroll; position: absolute; top: -9999px;'; document.body.appendChild(scrollp); var scrollbarWidth = scrollp.offsetWidth - scrollp.clientWidth; document.body.removeChild(scrollp); return scrollbarWidth; }
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SummaryUse JS to implement a The function may not be difficult, but as programmers, you should always think about how to implement this function more simply and elegantly, and always focus on improving the user experience. Forconditional judgment
        precautions for js to capture the page scroll bar? following is a practical case, let’s take look. <>, maybe ten lines of logical judgment may only require one line. I have been deeply impressed recently, and I must be good at using ternaryexpressionsif..elseThe principle is to judge whether the document height is greater than the
       visual area
       height.
       Recommended reading:
       
Detailed explanation of the three types of $() in jQuery
       
How to choose the jQuery version
       

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