


The Back to Top component is an extremely common web page function with a simple requirement: after the page scrolls a certain distance, a Back to Top button is displayed. Clicking this button can scroll the scroll bar back to the beginning of the page.
The implementation idea is also very easy, just change the value of document.documentElement.scrollTop or document.body.scrollTop.
This article abandons all the cool effects of acceleration and deceleration, returns to the essence of software, and provides the simplest implementation. It only pursues practicality and does not pursue the so-called user experience. The effect is as follows
Since the idea and code are very simple, I will directly post the implementation details:
var BackTop = function (domE,distance) { if (!domE) return; var _onscroll = window.onscroll, _onclick = domE.onclick; window.onscroll = throttle(function(){ typeof _onscroll === 'function' && _onscroll.apply(this, arguments); toggleDomE(); },100); domE.onclick = function(){ typeof _onclick === 'function' && _onclick.apply(this, arguments); document.documentElement.scrollTop = 0; document.body.scrollTop = 0; }; function toggleDomE(){ domE.style.display = (document.documentElement.scrollTop || document.body.scrollTop) > (distance || 500) ? 'block' : 'none'; } function throttle(func, wait) { var timer = null; return function () { var self = this, args = arguments; if (timer) clearTimeout(timer); timer = setTimeout(function () { return typeof func === 'function' && func.apply(self, args); }, wait); } } };
Calling method:
<script> new BackTop(document.getElementById('backTop')) </script>
The reason why I wrote this blog and made such a simple thing is for two reasons:
1) I have been writing some common simple components by hand during this time. This is the simpler of the simple. In order to make this series of blogs more complete, I added this component;
2) I want to express one of my views in the work process: don’t use user experience to decorate your software or products. To put it bluntly, user experience can be divided into two words, one is good impression, and the other is good impression. It's just fun, but this is not the ultimate goal of product development and operation. No matter how beautiful you make things, if the core value and service of the product are not enough, even if you make the function of returning to the top into a super invincible rocket, it will be in vain. . When doing front-end development, you have to exercise some control over the degree to which the product manager blindly mentions user experience functions. For this component, I think it is redundant to do acceleration or deceleration effects. It not only increases development time, but also delays users' time and abandons themselves. The stubbornness in playing with technology can make your work more perfect.
Let me share with you some common web page return to top codes
1. It is easiest to use HTML anchor tags
But the only drawback is that the style is not very good and this anchor tag will be displayed.
You can place it anywhere after the
tag, as long as it is close to the top.Place at the bottom of the page:
2. Use Javascript Scroll function to return to the top
The scroll function is used to control the position of the scroll bar. There are two very simple implementation methods:
Method 1 (recommended: simple and convenient):
The first parameter of scroll is the horizontal position, and the second parameter is the vertical position. For example, if you want to position it at 50 pixels vertically, just change it to scroll(0,50).
Method 2 (focus on effect: slowly upward):
This method is a gradual return to the top, which should look better. The code is as follows:
functionpageScroll() {window.scrollBy(0,-10);scrolldelay=setTimeout('pageScroll()',100);}<ahref="pageScroll();">返回顶部</a>
This will dynamically return to the top, but although it returns to the top, the code is still running, and you need to add a sentence to the pageScroll function to stop it.
if(document.documentElement.scrollTop==0)clearTimeout(scrolldelay);
3. Use Onload plus scroll function to dynamically return to the top
First add:
before the end of the body tag of the web page<divid="gotop">返回顶部</div>
2. Then call the following JS script part:
BackTop=function(btnId){varbtn=document.getElementById(btnId);vard=document.documentElement;window.onscroll=set;btn.onclick=function(){btn.style.display="none";window.onscroll=null;this.timer=setInterval(function(){d.scrollTop-=Math.ceil(d.scrollTop*0.1);if(d.scrollTop==0)clearInterval(btn.timer,window.onscroll=set);},10);};functionset(){btn.style.display=d.scrollTop?'block':"none"}};BackTop('gotop');
These can be placed in a web page, or can be saved independently as a js file, such as gotop.js, and then in the following form:
<scriptsrc="/js/gotop.js"type=text/javascript></script>
to call. Of course, it is best to place it under the "Return to Top" label. This calling method assumes that the file path is JS. Please modify it according to the actual situation when placing it in other locations.

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Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

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Different JavaScript engines have different effects when parsing and executing JavaScript code, because the implementation principles and optimization strategies of each engine differ. 1. Lexical analysis: convert source code into lexical unit. 2. Grammar analysis: Generate an abstract syntax tree. 3. Optimization and compilation: Generate machine code through the JIT compiler. 4. Execute: Run the machine code. V8 engine optimizes through instant compilation and hidden class, SpiderMonkey uses a type inference system, resulting in different performance performance on the same code.

JavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.

I built a functional multi-tenant SaaS application (an EdTech app) with your everyday tech tool and you can do the same. First, what’s a multi-tenant SaaS application? Multi-tenant SaaS applications let you serve multiple customers from a sing


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