javascript

仅使用CSS就可以提高页面渲染速度的4个技巧

随声附和 提交于 2021-02-20 16:16:19
文末福利资源更新 本文将重点介绍4个可以用来提高页面渲染速度的CSS技巧。 1. Content-visibility 一般来说,大多数Web应用都有复杂的UI元素,它的扩展范围超出了用户在浏览器视图中看到的内容。在这种情况下,我们可以使用内容可见性( content-visibility )来跳过屏幕外内容的渲染。如果你有大量的离屏内容,这将大大减少页面渲染时间。 这个功能是最新增加的功能之一,也是对提高渲染性能影响最大的功能之一。虽然 content-visibility 接受几个值,但我们可以在元素上使用 content-visibility: auto; 来获得直接的性能提升。 让我们考虑一下下面的页面,其中包含许多不同信息的卡片。虽然大约有12张卡适合屏幕,但列表中大约有375张卡。正如你所看到的,浏览器用了1037ms来渲染这个页面 。 下一步,您可以向所有卡添加 content-visibility 。 在这个例子中,在页面中加入 content-visibility 后,渲染时间下降到150ms,这是6倍以上的性能提升。 正如你所看到的,内容可见性是相当强大的,对提高页面渲染时间非常有用。根据我们目前所讨论的东西,你一定是把它当成了页面渲染的银弹。 content-visibility 的限制 然而,有几个领域的内容可视性不佳。我想强调两点,供大家参考。

Best possible combination sum of predefined numbers that smaller or equal NN

淺唱寂寞╮ 提交于 2021-02-20 15:28:51
问题 I have a list of lengths for pipes and I need fit these lengths within maximum allowed length for the best yield For example the max allowed length is 90 and the pieces I need to make are: 25, 60, 13, 48, 23, 29, 27, 22 For the best fit within 90 I'd have a group of these numbers: 60, 29 (89 total) 27, 25, 13, 23 (88 total) 48, 22 (70 total) I found this answer to similar question, but I don't know how to convert it to use in excel or javascript or php Any help would be appreciated. Thank you

Best possible combination sum of predefined numbers that smaller or equal NN

非 Y 不嫁゛ 提交于 2021-02-20 15:24:10
问题 I have a list of lengths for pipes and I need fit these lengths within maximum allowed length for the best yield For example the max allowed length is 90 and the pieces I need to make are: 25, 60, 13, 48, 23, 29, 27, 22 For the best fit within 90 I'd have a group of these numbers: 60, 29 (89 total) 27, 25, 13, 23 (88 total) 48, 22 (70 total) I found this answer to similar question, but I don't know how to convert it to use in excel or javascript or php Any help would be appreciated. Thank you

Best possible combination sum of predefined numbers that smaller or equal NN

℡╲_俬逩灬. 提交于 2021-02-20 15:18:23
问题 I have a list of lengths for pipes and I need fit these lengths within maximum allowed length for the best yield For example the max allowed length is 90 and the pieces I need to make are: 25, 60, 13, 48, 23, 29, 27, 22 For the best fit within 90 I'd have a group of these numbers: 60, 29 (89 total) 27, 25, 13, 23 (88 total) 48, 22 (70 total) I found this answer to similar question, but I don't know how to convert it to use in excel or javascript or php Any help would be appreciated. Thank you

javascript beginner: add a dynamic style in javascript? [duplicate]

柔情痞子 提交于 2021-02-20 13:54:49
问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: How to create a <style> tag with Javascript I write a dynamic form using java-script. I want to add the style in java-script itself. I write some code to add a style. But it is not working.This is the code am write in my project. var sheet = document.createElement('style'); sheet.type="text/css"; sheet.innerHTML = "body{color:red;}"; document.body.appendChild(sheet); Anyone help me please. 回答1: Your code is fine

why instanceof keeps saying true after prototype changed?

此生再无相见时 提交于 2021-02-20 13:53:14
问题 The instanceof operator should look at the prototype, no? Why does it not change its answer after the object's prototype has been changed? Example below: // The .prototype of objects created with 'new MyKlass' // is MyKlass.prototype var MyKlass = function(name, age) { this.name = name; this.age = age; } var xx = new MyKlass('xx', 20); console.log(xx instanceof MyKlass); // true, OK xx.prototype = new String('s'); console.log(xx instanceof MyKlass); // also true, WHY??? 回答1: This case is

仅使用CSS就可以提高页面渲染速度的4个技巧

我与影子孤独终老i 提交于 2021-02-20 13:52:19
本文将重点介绍4个可以用来提高页面渲染速度的CSS技巧。 1. Content-visibility 一般来说,大多数Web应用都有复杂的UI元素,它的扩展范围超出了用户在浏览器视图中看到的内容。在这种情况下,我们可以使用内容可见性( content-visibility )来跳过屏幕外内容的渲染。如果你有大量的离屏内容,这将大大减少页面渲染时间。 这个功能是最新增加的功能之一,也是对提高渲染性能影响最大的功能之一。虽然 content-visibility 接受几个值,但我们可以在元素上使用 content-visibility: auto; 来获得直接的性能提升。 让我们考虑一下下面的页面,其中包含许多不同信息的卡片。虽然大约有12张卡适合屏幕,但列表中大约有375张卡。正如你所看到的,浏览器用了1037ms来渲染这个页面 。 下一步,您可以向所有卡添加 content-visibility 。 在这个例子中,在页面中加入 content-visibility 后,渲染时间下降到150ms,这是6倍以上的性能提升。 正如你所看到的,内容可见性是相当强大的,对提高页面渲染时间非常有用。根据我们目前所讨论的东西,你一定是把它当成了页面渲染的银弹。 content-visibility 的限制 然而,有几个领域的内容可视性不佳。我想强调两点,供大家参考。 此功能仍处于试验阶段。

why instanceof keeps saying true after prototype changed?

独自空忆成欢 提交于 2021-02-20 13:51:56
问题 The instanceof operator should look at the prototype, no? Why does it not change its answer after the object's prototype has been changed? Example below: // The .prototype of objects created with 'new MyKlass' // is MyKlass.prototype var MyKlass = function(name, age) { this.name = name; this.age = age; } var xx = new MyKlass('xx', 20); console.log(xx instanceof MyKlass); // true, OK xx.prototype = new String('s'); console.log(xx instanceof MyKlass); // also true, WHY??? 回答1: This case is

bootstrap tab选项卡

吃可爱长大的小学妹 提交于 2021-02-20 13:51:43
<!DOCTYPE html> <html> <head> <meta charset= " utf-8 " > <title>个人中心2</title> <link rel= " stylesheet " type= " text/css " href= " css/bootstrap.min.css " /> <script src= " https://libs.baidu.com/jquery/2.0.0/jquery.min.js " ></script> <script src= " js/bootstrap.min.js " type= " text/javascript " charset= " utf-8 " ></script> </head> <body> <ul class = " nav nav-tabs " > <li role= " presentation " class = " active " ><a href= " #menu1 " data-toggle= " tab " >Home</a></li> <li role= " presentation " ><a href= " #menu2 " data-toggle= " tab " >Profile</a></li> <li role= " presentation " ><a href

从微信小程序到鸿蒙js开发【07】——menu&toast&dialog

ε祈祈猫儿з 提交于 2021-02-20 12:51:46
目录: 1、menu弹出菜单 2、Toast提示框 3、prompt模块的对话框dialog 4、dialog对话框组件 1、menu弹出菜单 这是微信小程序没有的一个组件,提供了一个可唤起的轻量级弹出菜单。menu的子组件为option。 <menu id="userMenu" onselected="menuSelect"> <option value="login">登录</option> <option value="register">注册</option> </menu> 在hml中写好菜单,但这时启动app是不会显示出来的,且不会占用任何页面空间。 menu需要在方法中被唤起,因此需要设置id属性。这里通过点击“点击登录/注册“文本框唤起菜单: <text if="{{ !userInfo }}" onclick="showUserMenu" class="info_hint"> 点击登录/注册 </text> showUserMenu() { this.$element("userMenu").show(); } 使用无参的show()方法,菜单在页面的左上角被唤起弹出。 show方法还有一个重载方法,可以设置菜单弹出的x轴和y轴偏移量。x和y需要给数值类型,单位为px。 showUserMenu() { this.$element("userMenu").show