A very useful one-line JavaScript code

1. Date processing

1. Is the inspection date valid?

This method is used to check whether the given date is valid:

javascript

const isDateValid = (...val) => !Number.isNaN(new Date(...val).valueOf());

isDateValid("December 17, 1995 03:24:00");  // true

2. Calculate the interval between two dates

This method is used to calculate the time between two dates:

javascript

const dayDif = (date1, date2) => Math.ceil(Math.abs(date1.getTime() - date2.getTime()) / 86400000)

dayDif(new Date("2021-11-3"), new Date("2022-2-1"))  // 90

There are still 90 days until Chinese New Year~

3. Find the day of the year a date falls on

Calculate the ordinal from local calendar fields, using UTC date differences to avoid daylight-saving shifts.

javascript

const dayOfYear = date => Math.floor(
  (Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()) -
   Date.UTC(date.getFullYear(), 0, 0)) / 86400000
);

dayOfYear(new Date());   // 307

More than 300 days have passed in 2021~

4. time formatting

This method can be used to convert time into hour:minutes:seconds format:

javascript

const timeFromDate = date => date.toTimeString().slice(0, 8);

timeFromDate(new Date(2021, 11, 2, 12, 30, 0));  // 12:30:00
timeFromDate(new Date());  // 返回当前时间 09:00:00

2. String processing

1. Capitalize the first letter of a string

This method is used to capitalize the first letter of an English string:

javascript

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1)

capitalize("hello world")  // Hello world

2. flip string

This method is used to flip a string and return the flipped string:

javascript

const reverse = str => str.split('').reverse().join('');

reverse('hello world');   // 'dlrow olleh'

3. random string

This method is used to generate a random string:

javascript

const randomString = () => Math.random().toString(36).slice(2);

randomString();

4. truncate string

This method truncates a string at a specified length:

javascript

const truncateString = (string, length) => string.length < length ? string : `${string.slice(0, length - 3)}...`;

truncateString('Hi, I should be truncated because I am too loooong!', 36)   // 'Hi, I should be truncated because...'

5. Remove HTML from string

This method is used to remove HTML elements from a string:

javascript

const stripHtml = html => (new DOMParser().parseFromString(html, 'text/html')).body.textContent || '';

3. Array processing

1. Remove duplicates from array

This method is used to remove duplicates from an array:

javascript

const removeDuplicates = (arr) => [...new Set(arr)];

console.log(removeDuplicates([1, 2, 2, 3, 3, 4, 4, 5, 5, 6]));

2. Determine whether the array is empty

This checks whether an array is nonempty; non-array inputs return false.

javascript

const isNotEmpty = arr => Array.isArray(arr) && arr.length > 0;

isNotEmpty([1, 2, 3]);  // true

3. Merge two arrays

You can use the following two methods to merge two arrays:

javascript

const merge = (a, b) => a.concat(b);

const mergeWithSpread = (a, b) => [...a, ...b];

4. Digital operations

1. Determine whether a number is odd or even

This method is used to determine whether a number is odd or even:

javascript

const isEven = num => num % 2 === 0;

isEven(996);

2. Get the average of a set of numbers

javascript

const average = (...args) => args.reduce((a, b) => a + b) / args.length;

average(1, 2, 3, 4, 5);   // 3

3. Get a random integer between two integers

This method is used to get a random integer between two integers

javascript

const random = (min, max) => Math.floor(Math.random() * (max - min + 1) + min);

random(1, 50);

4. Round to specified digits

This method is used to round a number to the specified number of places:

javascript

const round = (n, d) => Number(Math.round(n + "e" + d) + "e-" + d)

round(1.005, 2) //1.01
round(1.555, 2) //1.56

5. Color operation

1. Convert RGB to sixteen mechanism

This method can convert an RGB color value into a hexadecimal value:

javascript

const rgbToHex = (r, g, b) => "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);

rgbToHex(255, 255, 255);  // '#ffffff'

2. Get random hex color

This method is used to obtain a random hexadecimal color value:

javascript

const randomHex = () => "#" + Math.floor(Math.random() * 0x1000000).toString(16).padStart(6, "0");

randomHex();

6. Browser operation

1. Copy content to clipboard

This method uses navigator.clipboard.writeText to copy text to the clipboard:

javascript

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

copyToClipboard("Hello World");

2. Clear all cookies

This example only attempts to delete script-visible cookies matching the root path; it cannot delete HttpOnly cookies or every path/domain variant.

javascript

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

3. Get selected text

This method gets the text selected by the user through the built-in getSelection property:

javascript

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

getSelectedText();

4. Check if it is dark mode

This method is used to detect whether the current environment is in dark mode. It is a Boolean value:

javascript

const isDarkMode = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches

console.log(isDarkMode)

5. Scroll to top of page

This method is used to return to the top of the page:

javascript

const goToTop = () => window.scrollTo(0, 0);

goToTop();

6. Determine whether the current tab page is active

This method is used to detect whether the current tab has been activated:

javascript

const isTabInView = () => !document.hidden;

7. Determine whether the current device is an Apple device

This method is used to detect whether the current device is an Apple device:

javascript

const isAppleDevice = () => /Mac|iPod|iPhone|iPad/.test(navigator.platform);

isAppleDevice();

8. Whether to scroll to the bottom of the page

This method is used to determine whether the page has reached the bottom:

javascript

const scrolledToBottom = () => document.documentElement.clientHeight + window.scrollY >= document.documentElement.scrollHeight;

9. Redirect to a URL

This method is used to redirect to a new URL:

javascript

const redirect = url => location.href = url

redirect("https://www.google.com/")

10. Open browser print box

This method is used to open the browser's print box:

javascript

const showPrintDialog = () => window.print()

7. Other operations

1. random boolean

This method can return a random Boolean value. Use Math.random() to get a random number from 0 to 1. Compared with 0.5, there is a half probability of getting a true or false value.

javascript

const randomBoolean = () => Math.random() >= 0.5;

randomBoolean();

2. variable exchange

You can use the following form to swap the values of two variables without using a third variable:

javascript

[foo, bar] = [bar, foo];

3. Get the type of variable

This method is used to get the type of a variable:

javascript

const trueTypeOf = (obj) => Object.prototype.toString.call(obj).slice(8, -1).toLowerCase();

trueTypeOf('');     // string
trueTypeOf(0);      // number
trueTypeOf();       // undefined
trueTypeOf(null);   // null
trueTypeOf({});     // object
trueTypeOf([]);     // array
trueTypeOf(0);      // number
trueTypeOf(() => {});  // function

4. Conversion between Fahrenheit and Celsius

This method is used to convert between Celsius and Fahrenheit:

javascript

const celsiusToFahrenheit = (celsius) => celsius * 9/5 + 32;
const fahrenheitToCelsius = (fahrenheit) => (fahrenheit - 32) * 5/9;

celsiusToFahrenheit(15);    // 59
celsiusToFahrenheit(0);     // 32
celsiusToFahrenheit(-20);   // -4
fahrenheitToCelsius(59);    // 15
fahrenheitToCelsius(32);    // 0

5. Check if the object is empty

This method is used to detect whether a JavaScript object is empty:

javascript

const isEmpty = obj => Reflect.ownKeys(obj).length === 0 && obj.constructor === Object;

Regular basic syntax

^ 匹配一个输入或一行的开头，/^a/匹配"an A"，而不匹配"An a" 
$ 匹配一个输入或一行的结尾，/a$/匹配"An a"，而不匹配"an A" 
* 匹配前面元字符0次或多次，/ba*/将匹配b,ba,baa,baaa 
+ 匹配前面的表达式 1 次或多次，如 /ba+/ 匹配 ba、baa，不匹配单独的 b。
? 匹配前面的表达式 0 次或 1 次，如 /ba?/ 匹配 b、ba；紧跟量词时表示非贪婪匹配。
(x) 是捕获组；反向引用如 /([ab])\\1/，字面括号应转义为 \\( 与 \\)。
x|y 匹配x或y 
{n} 精确匹配n次 
{n,} 匹配n次以上 
{n,m} 匹配n-m次 
[xyz] 字符集(character set)，匹配这个集合中的任一一个字符(或元字符) 
[^xyz] 不匹配这个集合中的任何一个字符 
[a-z] 字符范围。匹配指定范围内的任意字符。例如，“[a-z]”可以匹配“a”到“z”范围内的任意小写字母字符。
[^a-z] 负值字符范围。匹配任何不在指定范围内的任意字符。例如，“[^a-z]”可以匹配任何不在“a”到“z”范围内的任意字符。
. 匹配除“\n”之外的任何单个字符。要匹配包括“\n”在内的任何字符，请使用像“(.|\n)”的模式。
[\b] 匹配一个退格符 
\b 匹配一个单词的边界 
\B 匹配一个单词的非边界 
\cX 这儿，X是一个控制符，/\cM/匹配Ctrl-M 
\d 匹配一个字数字符，/\d/ = /[0-9]/ 
\D 匹配一个非字数字符，/\D/ = /[^0-9]/ 
\f 匹配一个换页符。等价于\x0c和\cL。
\n 匹配一个换行符 等价于\x0a和\cJ。
\r 匹配一个回车符 等价于\x0d和\cM。
\s 匹配一个空白字符，包括\n,\r,\f,\t,\v等 。等价于[ \f\n\r\t\v]。
\S 匹配一个非空白字符，等于/[^\n\f\r\t\v]/ 。[^ \f\n\r\t\v]。
\t 匹配一个制表符 。等价于\x09和\cI。
\v 匹配一个垂直制表符 等价于\x0b和\cK。
\\w 匹配 ASCII 字母、数字和下划线，基本等价于 [A-Za-z0-9_]。
\\W 匹配不属于 \\w 的字符，基本等价于 [^A-Za-z0-9_]。
\xn 匹配n，其中n为十六进制转义值。十六进制转义值必须为确定的两个数字长。例如，“\x41”匹配“A”。“\x041”则等价于“\x04&1”。正则表达式中可以使用ASCII编码。
\num 匹配num，其中num是一个正整数。对所获取的匹配的引用。例如，“(.)\1”匹配两个连续的相同字符。
\n 标识一个八进制转义值或一个向后引用。如果\n之前至少n个获取的子表达式，则n为向后引用。否则，如果n为八进制数字（0-7），则n为一个八进制转义值。
\nm 标识一个八进制转义值或一个向后引用。如果\nm之前至少有nm个获得子表达式，则nm为向后引用。如果\nm之前至少有n个获取，则n为一个后跟文字m的向后引用。如果前面的条件都不满足，若n和m均为八进制数字（0-7），则\nm将匹配八进制转义值nm。
\nml 如果n为八进制数字（0-3），且m和l均为八进制数字（0-7），则匹配八进制转义值nml。
\un 匹配n，其中n是一个用四个十六进制数字表示的Unicode字符。例如，\u00A9匹配版权符号（©）。

The difference between .* and .*? is that the former is a greedy matching mode and the latter is a non-greedy matching mode.The same goes for .+ and .+?


(x)	
像下面的例子展示的那样，它会匹配 'x' 并且记住匹配项。其中括号被称为捕获括号。

模式 /(foo) (bar) \1 \2/ 中的 '(foo)' 和 '(bar)' 匹配并记住字符串 "foo bar foo bar" 中前两个单词。模式中的 \1 和 \2 表示第一个和第二个被捕获括号匹配的子字符串，即 foo 和 bar，匹配了原字符串中的后两个单词。注意 \1、\2、...、\n 是用在正则表达式的匹配环节，详情可以参阅后文的 \n 条目。而在正则表达式的替换环节，则要使用像 $1、$2、...、$n 这样的语法，例如，'bar foo'.replace(/(...) (...)/, '$2 $1')。$& 表示整个用于匹配的原字符串。
---------------------------------------
(?:x)	
匹配 'x' 但是不记住匹配项。这种括号叫作非捕获括号，使得你能够定义与正则表达式运算符一起使用的子表达式。看看这个例子 /(?:foo){1,2}/。如果表达式是 /foo{1,2}/，{1,2} 将只应用于 'foo' 的最后一个字符 'o'。如果使用非捕获括号，则 {1,2} 会应用于整个 'foo' 单词。更多信息，可以参阅下文的 Using parentheses 条目.
---------------------------------------
x(?=y)	
匹配'x'仅仅当'x'后面跟着'y'.这种叫做先行断言。

例如，/Jack(?=Sprat)/会匹配到'Jack'仅仅当它后面跟着'Sprat'。/Jack(?=Sprat|Frost)/匹配‘Jack’仅仅当它后面跟着'Sprat'或者是‘Frost’。但是‘Sprat’和‘Frost’都不是匹配结果的一部分。
---------------------------------------
(?<=y)x	
匹配'x'仅仅当'x'前面是'y'.这种叫做后行断言。

例如，/(?<=Jack)Sprat/会匹配到' Sprat '仅仅当它前面是' Jack '。/(?<=Jack|Tom)Sprat/匹配‘ Sprat ’仅仅当它前面是'Jack'或者是‘Tom’。但是‘Jack’和‘Tom’都不是匹配结果的一部分。
---------------------------------------
x(?!y)	
仅仅当'x'后面不跟着'y'时匹配'x'，这被称为正向否定查找。

例如，仅仅当这个数字后面没有跟小数点的时候，/\d+(?!\.)/ 匹配一个数字。正则表达式/\d+(?!\.)/.exec("3.141")匹配‘141’而不是‘3.141’
---------------------------------------
(?<!y)x	
仅仅当'x'前面不是'y'时匹配'x'，这被称为反向否定查找。

例如, 仅仅当这个数字前面没有负号的时候，/(?<!-)\d+/ 匹配一个数字。
/(?<!-)\d+/.exec('3') 匹配到 "3".
/(?<!-)\d+/.exec('-3') 因为这个数字前有负号，所以没有匹配到。
---------------------------------------
x|y	
匹配‘x’或者‘y’。

例如，/green|red/匹配“green apple”中的‘green’和“red apple”中的‘red’

Application summary

Verify whether consecutive numbers are repeated

"bcae1958fiefadf1958fef".match(/^.*?(\d{4})(?:(?!\1).)*\1/)

Verify if there are duplicate characters


"bcae1958fiqpdljwrxy".match(/^.*?(\w)(?:(?!\1).)*\1/)

IP address regularity

/^((([1-9]?\d)|(1\d\d)|(2[0-4]\d)|(25[0-5]))\.){3}(([1-9]?\d)|(1\d\d)|(2[0-4]\d)|(25[0-5]))$/.test('0.255.255.0')

12 digits, 6 consecutive identical digits cannot appear in it


'123777890987'.match(/^(?:([0-9])(?!\1{5})){12}$/)

10 non-repeating letters within A-Z

Method one:

/^(?:([A-Z])(?!.*?\1)){10}$/.test("ABCDEFGHIJ");

Method two:

'asdfghjklp'.match(/^(?:([a-z])(?=((?!\1).)*$)){10}$/)

Thousands separator (js implementation)


function thousandBitSeparator(num) {
    if (!Number.isFinite(num)) throw new TypeError('Expected a finite number');
    const [integer, fraction] = String(num).split('.');
    const grouped = integer.replace(/\B(?=(\d{3})+(?!\d))/g, ',');
    return fraction === undefined ? grouped : grouped + '.' + fraction;
}
console.log(thousandBitSeparator(-1234567.9012));


var a = 1;
function b(){
    var a=2;
    function c(){
        console.log(a)
    }
    return c;
}

b()();

Author: CUGGZ Link: https://juejin.cn/post/7025771605422768159

1. Date processing ​

1. Is the inspection date valid? ​

2. Calculate the interval between two dates ​

3. Find the day of the year a date falls on ​

4. time formatting ​

2. String processing ​

1. Capitalize the first letter of a string ​

2. flip string ​

3. random string ​

4. truncate string ​

5. Remove HTML from string ​

3. Array processing ​

1. Remove duplicates from array ​

2. Determine whether the array is empty ​

3. Merge two arrays ​

4. Digital operations ​

1. Determine whether a number is odd or even ​

2. Get the average of a set of numbers ​

3. Get a random integer between two integers ​

4. Round to specified digits ​

5. Color operation ​

1. Convert RGB to sixteen mechanism ​

2. Get random hex color ​

6. Browser operation ​

1. Copy content to clipboard ​

2. Clear all cookies ​

3. Get selected text ​

4. Check if it is dark mode ​

5. Scroll to top of page ​

6. Determine whether the current tab page is active ​

7. Determine whether the current device is an Apple device ​

8. Whether to scroll to the bottom of the page ​

9. Redirect to a URL ​

10. Open browser print box ​

7. Other operations ​

1. random boolean ​

2. variable exchange ​

3. Get the type of variable ​

4. Conversion between Fahrenheit and Celsius ​

5. Check if the object is empty ​

Regular basic syntax ​

Application summary ​

Verify whether consecutive numbers are repeated ​

Verify if there are duplicate characters ​

IP address regularity ​

12 digits, 6 consecutive identical digits cannot appear in it ​

10 non-repeating letters within A-Z ​

Thousands separator (js implementation) ​

1. Date processing

1. Is the inspection date valid?

2. Calculate the interval between two dates

3. Find the day of the year a date falls on

4. time formatting

2. String processing

1. Capitalize the first letter of a string

2. flip string

3. random string

4. truncate string

5. Remove HTML from string

3. Array processing

1. Remove duplicates from array

2. Determine whether the array is empty

3. Merge two arrays

4. Digital operations

1. Determine whether a number is odd or even

2. Get the average of a set of numbers

3. Get a random integer between two integers

4. Round to specified digits

5. Color operation

1. Convert RGB to sixteen mechanism

2. Get random hex color

6. Browser operation

1. Copy content to clipboard

2. Clear all cookies

3. Get selected text

4. Check if it is dark mode

5. Scroll to top of page

6. Determine whether the current tab page is active

7. Determine whether the current device is an Apple device

8. Whether to scroll to the bottom of the page

9. Redirect to a URL

10. Open browser print box

7. Other operations

1. random boolean

2. variable exchange

3. Get the type of variable

4. Conversion between Fahrenheit and Celsius

5. Check if the object is empty

Regular basic syntax

Application summary

Verify whether consecutive numbers are repeated

Verify if there are duplicate characters

IP address regularity

12 digits, 6 consecutive identical digits cannot appear in it

10 non-repeating letters within A-Z

Thousands separator (js implementation)