Front-End Code Snippets Worth Checking Out

In daily development, we will accumulate some commonly used code snippets, which can be directly copied and pasted into various projects for use, which is very convenient. If you have taken over other people's projects, you may notice that the same tools and methods exist in some projects. These are common code snippets accumulated by previous developers.

Now that the front-end community has matured, excellent libraries such as lodash and dayjs can meet our needs for processing arrays, dates, etc. This article will not repeat these common fragments.

1. Detect click outside element

When hiding the pop-up box or collapsing the drop-down menu, use the contains method instead of checking layer by layer.

// 代码示例 (此处省略)

2. Quickly open the official website

To view the homepage or code repository of a third-party library, you can use these npm commands:

Open homepage

npm home PACKAGE_NAME

For example, for React

npm home react

Open the code repository

npm repo PACKAGE_NAME

For example, for React

npm repo react

3. One-time event listener

In addition to removing the listener in the event function, you can also use the once parameter.

// 代码示例 (此处省略)

4. Format seconds as HH:mm:ss

In scenarios such as displaying audio/video duration, you can format seconds like this:

const formatSeconds = (s) =>
  [parseInt(s / 60 / 60), parseInt((s / 60) % 60), parseInt(s % 60)].join(":").replace(/\b(\d)\b/g, "0");
const seconds = 3661;
console.log(formatSeconds(seconds));

To display relative time like "just now", you can try the timeago.js library.

5. Convert URL parameters to objects

No need to use query-string library, use URLSearchParams API directly:

const getUrlParams = (query) =>
  Array.from(new URLSearchParams(query)).reduce(
    (p, [k, v]) => Object.assign({}, p, { [k]: p[k] ? (Array.isArray(p[k]) ? p[k] : [p[k]]).concat(v) : v }),
    {}
  );
const query = "?a=1&b=2&a=3";
console.log(getUrlParams(query));

6. Open new tab

When opening external links, set rel="noopener noreferrer" to avoid security risks.

<a href="https://example.com" rel="noopener noreferrer" target="_blank">打开</a>

function openNewTab() {
  window.open("https://example.com", "newTab", "noopener,noreferrer");
}

7. Show uploaded images

Use the readAsDataURL method of the FileReader API to display the uploaded image.

// 代码示例 (此处省略)

8. File download

Using the download attribute of the tag can trigger a download, but it has some limitations.

<a download="" href="https://www.php.cn/link/8b89afaf8e00e0a46ea4d76ac473b1a2">下载</a>

function download(url) {
  const link = document.createElement("a");
  link.download = "file name";
  link.href = url;
  document.body.appendChild(link);
  link.click();
  document.body.removeChild(link);
}

You can also set response headers on the server side, or on the browser side using Blob and createObjectURL.

const data = JSON.stringify({ message: "Hello" });
const blob = new Blob([data], { type: "application/json" });
const url = window.URL.createObjectURL(blob);
download(url);
window.URL.revokeObjectURL(url);

9. Cached results

Cache function results for complex calculations.

const memoize = (fn) =>
  (
    (cache = Object.create(null)) =>
    (arg) =>
      cache[arg] || (cache[arg] = fn(arg))
  )();
// 代码示例 (此处省略)

10. Multi-line ellipsis

Use CSS to truncate text to ellipses, on single or multiple lines.

.truncate-single {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.truncate-multi {
  display: -webkit-box;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 2;
  overflow: hidden;
}

11. Select the last few elements

Use CSS selectors to target specific elements.

li:nth-child(-n + 3) {
  text-decoration: underline;
}
// 代码示例 (此处省略)

12. Scroll bar style

Customize scroll bar styles using CSS or third-party libraries like better-scroll.

// 代码示例 (此处省略)

13. Percentage Calculation-Maximum Remainder Method

Use the maximum remainder method to ensure that the percentages sum to 1.

// 代码示例 (此处省略)

14. Limit concurrency

Limit the number of concurrent requests when making a large number of requests.

const formatSeconds = (s) =>
  [parseInt(s / 60 / 60), parseInt((s / 60) % 60), parseInt(s % 60)].join(":").replace(/\b(\d)\b/g, "0");
const seconds = 3661;
console.log(formatSeconds(seconds));

15. UUID generation

Use this code to generate a unique identifier.

const getUrlParams = (query) =>
  Array.from(new URLSearchParams(query)).reduce(
    (p, [k, v]) => Object.assign({}, p, { [k]: p[k] ? (Array.isArray(p[k]) ? p[k] : [p[k]]).concat(v) : v }),
    {}
  );
const query = "?a=1&b=2&a=3";
console.log(getUrlParams(query));

16. Open modal and prevent body from scrolling

Prevent body scrolling when opening the modal.

<a href="https://example.com" rel="noopener noreferrer" target="_blank">打开</a>

Original link: https://www.php.cn/link/d9d838896ca0a5e16e7efa2439943fbd

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