Key Points of Responsive Web Design (RWD)

Responsive web design (RWD) is essential to ensure that the website is accessible and user-friendly on devices of various screen sizes. It was proposed by Ethan Marcotte in 2010, allowing a single website to work properly on any device, regardless of screen size or viewport size.

RWD uses a variety of techniques and methods, including HTML viewport meta tags, media queries, CSS viewport units, CSS columns, CSS Flexbox and Grid, and JavaScript RWD options. All of this has good browser support, with CSS Grid currently supported by nearly 95% of commonly used browsers.

Testing RWD and cross-browser compatibility is critical and can be done with in-browser testing, mobile operating system simulator, online testing services and real-world device testing. However, each method has its own limitations and should be used in combination to obtain the most accurate results.

Online testing services (such as LambdaTest) allow users to test responsive pages on mobile browsers over the web. These services can also include automated testing APIs for checking for style regression or corrupted user interfaces.

Real device testing is the most accurate way to test RWD because it allows evaluating actual processing speeds, touch controls, and overall design. It is recommended to test on as many devices as possible, especially general devices that have been used for one or two years.

How to work in RWD

There is no single RWD method or technique.

First, you have to determine how the website design will react to monitors of different sizes. This is a challenge, with many early RWD websites taking an existing desktop layout and removing some of the content with reduced screen size.

A better technology is "mobile first". It starts with a linear mobile view that runs on all devices and then rearranges or tweaks content when more space and supported browser features are available. Recently, many websites have adopted simpler layouts, where the mobile and desktop experiences are mostly similar.

A typical example of RWD is the hamburger menu. Users on smaller screens can click on the icon to view navigation links, while users on larger screens can see all the options in the horizontal list.

The following sections provide some technical implementation options.

HTML viewport meta tag

No matter what RWD technology is used, the following tags must be set in HTML:

<meta name="viewport" content="width=device-width, initial-scale=1">

width=device-width Settings ensure that the mobile browser scales the logical CSS pixels to the screen width. Without this setting, the browser assumes that it is rendering the desktop website and scaling accordingly so that it can pan and scale.

Media Query

Media query was the main basis of early RWD websites. They allow CSS to target a specific range of viewport sizes. For example:

<meta name="viewport" content="width=device-width, initial-scale=1">

Media queries are still in use, although less explicit options are available now.

<picture> Element

HTML <picture> Elements use media query syntax to control from multiple <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/173915575374245.jpg" class="lazy" alt="How to Test Responsive Web Design Cross-Browser Compatibility " /> </picture>

CSS viewport unit

CSS units vw and vh represent 1% of viewport width and height, respectively. vmin is 1% of the minimum size, and vmax is 1% of the maximum size.

These allow RWD flexibility, especially when used in conjunction with calc. For example:

/* 應(yīng)用于所有視圖的樣式 */
p {
  font-size: 1rem;
}

/* 應(yīng)用于寬度介于 900px 和 1200px 之間的視口的樣式 */
@media (min-width: 900px) and (max-width: 1200px) {
  p {
    font-size: 1.5rem;
  }
}

CSS column

CSS Multi-Column Layout provides a way to create multiple text columns as the container size increases. For example:

/* 字號隨視口寬度增加而增加 */
p {
  font-size: 1rem + 0.5vw;
}

CSS Flexbox and Grid

CSS Flexbox and CSS Grid provide modern technology to lay out child elements based on their content and available space. The main difference is:

• Flexbox is used for one-dimensional layout. Elements can be broken (or not broken) as needed, so the columns may not be aligned.
• Grid is used in two-dimensional layouts and usually has recognizable rows and columns.

Both can be used to create "intrinsic layouts" (a terminology invented by Jen Simmons). Essentially, the size of the element is determined based on the viewport size, without media queries. For example:

/*
列的最小寬度必須為 12rem
每個列之間有 2rem 的間隙
*/
.container {
  columns: 12rem auto;
  column-gap: 2rem;
}

JavaScript RWD Options

JavaScript can also be used to determine viewport size and react accordingly. For example:

/*
子元素將至少為 20rem 并填充行。
小于 20rem 的顯示將子元素大小調(diào)整為 1fr
(可用寬度的 100%)。

1rem 的間隙將始終圍繞元素。
*/
.grid-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(20rem, 1fr));
  grid-gap: 1rem;
}

Similarly, the size of a single element can be checked using offsetWidth and offsetHeight, although the getBoundingClientRect() method can return more information, including the decimal part of the pixel:

// 獲取視口寬度和高度
const vw = window.innerWidth, vh = window.innerHeight;

When the device rotates or the browser window is resized, the window and element size may change. matchMedia API can parse CSS media queries and trigger changes:

const element = document.getElementById('myelement'),
      rect = element.getBoundingClientRect(),
      ew = rect.width,
      eh = rect.height;

Browser support

The above RWD technologies all have good browser support. The latest option – CSS Grid – is currently supported by nearly 95% of commonly used browsers. However, it is still necessary to test your website on a variety of devices, resolutions and browsers...

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• In-browser test
• Mobile operating system emulator
• Online Testing Service (LambdaTest, etc.)
• Real Equipment Test
• One website, multiple views
• FAQs about responsive web design and cross-browser compatibility

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