2022 Recruitment Season | 15 Functions You Need to Master in Front-End Work

random array

Shuffling an array using the sort and random methods is very common.

const shuffleArray = (arr) => arr.sort(() => 0.5 - Math.random());
console.log(shuffleArray([1, 2, 3, 4])); 
// 结果：[ 1, 4, 3, 2 ]

Check if date is valid

Use the following code snippet to check if the given date is valid.

const isDateValid = (...val) => !Number.isNaN(new Date(...val).valueOf());
isDateValid("December 17, 1995 03:24:00"); 
// 结果：真

copy to clipboard

Copy any text to the clipboard navigator.clipboard.writeText .

const copyToClipboard = (text) => navigator.clipboard.writeText(text);
copyToClipboard("Hello World");

Find the day of the year

Find which day of a given date.

const dayOfYear = (date) =>
  Math.floor((date - new Date(date.getFullYear(), 0, 0)) / 1000 / 60 / 60 / 24);
dayOfYear(new Date());
// 结果：272

uppercase string

Javascript has no built-in uppercase function, so we can handle it with the following code.

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1)
capitalize("hello") 
// 结果：Hello

Find the number of days between two days

Use the following code snippet to find the number of days between 2 days.

const dayDif = (date1, date2) => Math.ceil(Math.abs(date1.getTime() - date2.getTime()) / 86400000)
dayDif(new Date("2020-10-21"), new Date("2021-10-22"))
// 结果：366

clear all cookies

All cookie stored on web pages can be easily cleared by document.cookie and clearing cookie .

const clearCookies = document.cookie.split(';').forEach(cookie => document.cookie = cookie.replace(/^ +/, '').replace(/=.*/, `=;expires=$ {new Date(0).toUTCString()};path=/`));

Generate random hex

Random hex colors can be generated using the Math.random and padEnd properties.

const randomHex = () => `#${Math.floor(Math.random() * 0xffffff).toString(16).padEnd(6, "0")}`;
console.log(randomHex()); 
// 结果：#92b008

remove duplicates from an array

Duplicates can be easily removed using Set .

const removeDuplicates = (arr) => [...new Set(arr)];
console.log(removeDuplicates([1, 2, 3, 3, 4, 4, 5, 5, 6])); 
// 结果：[ 1, 2, 3, 4, 5, 6 ]

Get query parameters from URL

Query parameters goole.com?search=easy&page=3 can be easily retrieved from URL , bypassing window.location or the original URL

const getParameters = (URL) => { 
  URL = JSON.parse('{"' + decodeURI(URL.split("?")[1]).replace(/"/g, '\\"').replace (/&/g, '","').replace(/=/g, '":"') +'"}'); 
  返回 JSON.stringify(URL); 
};
getParameters(window.location) 
// 结果：{ search : "easy", page : 3 }

record time from date

We can record the time in the format hour::minutes::seconds for a given date.

const timeFromDate = date => date.toTimeString().slice(0, 8);
console.log(timeFromDate(new Date(2021, 0, 10, 17, 30, 0))); 
// 结果：“17:30:00”

Check if a number is even or odd

const isEven = num => num % 2 === 0;
console.log(isEven(2)); 
// 结果：真

find the average of numbers

reduce uses the method to find the average between multiple numbers.

const average = (...args) => args.reduce((a, b) => a + b) / args.length;
average(1, 2, 3, 4);
// 结果：2.5

Check if array is empty

A simple function to check if the array is empty will return true or false .

const isNotEmpty = arr => Array.isArray(arr) && arr.length > 0;
isNotEmpty([1, 2, 3]); 
// 结果：真

get selected text

getSelection uses a built-in property to get the text selected by the user.

const getSelectedText = () => window.getSelection().toString();
getSelectedText();

Detect if in dark mode

Use the following code to check if the user's device is in dark mode.

const isDarkMode = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches
console.log(isDarkMode);
// 结果：真或假