30 seconds of code

Node

atob

解码使用 base-64 编码的数据字符串。

使用 base-64 编码为给定字符串创建 Buffer，并使用 Buffer.toString（'binary'） 返回已解码的字符串。

const atob = str => Buffer.from(str, 'base64').toString('binary');

示例代码

atob('Zm9vYmFy'); // 'foobar'

btoa

Creates a base-64 encoded ASCII string from a String object in which each character in the string is treated as a byte of binary data.

Create a Buffer for the given string with binary encoding and use Buffer.toString('base64') to return the encoded string.

创建 base-64 编码的 ASCII 字符串，其中字符串中的每个字符都被视为二进制数据的字节。

使用二进制编码为给定字符串创建 Buffer，并使用 Buffer.toString（'base64'） 返回编码字符串。

const btoa = str => Buffer.from(str, 'binary').toString('base64');

示例代码

btoa('foobar'); // 'Zm9vYmFy'

colorize

Add special characters to text to print in color in the console (combined with console.log()).

Use template literals and special characters to add the appropriate color code to the string output. For background colors, add a special character that resets the background color at the end of the string.

const colorize = (...args) => ({
  black: `\x1b[30m${args.join(' ')}`,
  red: `\x1b[31m${args.join(' ')}`,
  green: `\x1b[32m${args.join(' ')}`,
  yellow: `\x1b[33m${args.join(' ')}`,
  blue: `\x1b[34m${args.join(' ')}`,
  magenta: `\x1b[35m${args.join(' ')}`,
  cyan: `\x1b[36m${args.join(' ')}`,
  white: `\x1b[37m${args.join(' ')}`,
  bgBlack: `\x1b[40m${args.join(' ')}\x1b[0m`,
  bgRed: `\x1b[41m${args.join(' ')}\x1b[0m`,
  bgGreen: `\x1b[42m${args.join(' ')}\x1b[0m`,
  bgYellow: `\x1b[43m${args.join(' ')}\x1b[0m`,
  bgBlue: `\x1b[44m${args.join(' ')}\x1b[0m`,
  bgMagenta: `\x1b[45m${args.join(' ')}\x1b[0m`,
  bgCyan: `\x1b[46m${args.join(' ')}\x1b[0m`,
  bgWhite: `\x1b[47m${args.join(' ')}\x1b[0m`
});

向文本中添加特殊字符，以便在控制台中以彩色方式打印(与 console.log() 结合)。

使用模板字面量和特殊字符将相应的颜色代码添加到字符串输出中。对于有背景颜色的，添加一个特殊字符，在字符串的末尾重置背景颜色。

console.log(colorize('foo').red); // 'foo' (red letters)
console.log(colorize('foo', 'bar').bgBlue); // 'foo bar' (blue background)
console.log(colorize(colorize('foo').yellow, colorize('foo').green).bgWhite); // 'foo bar' (first word in yellow letters, second word in green letters, white background for both)

createDirIfNotExists

Creates a directory, if it does not exist.

Use fs.existsSync() to check if the directory exists, fs.mkdirSync() to create it.

const fs = require('fs');
const createDirIfNotExists = dir => (!fs.existsSync(dir) ? fs.mkdirSync(dir) : undefined);

示例代码

createDirIfNotExists('test'); // creates the directory 'test', if it doesn't exist

hasFlags

Check if the current process's arguments contain the specified flags.

Use Array.prototype.every() and Array.prototype.includes() to check if process.argv contains all the specified flags. Use a regular expression to test if the specified flags are prefixed with - or -- and prefix them accordingly.

const hasFlags = (...flags) =>
  flags.every(flag => process.argv.includes(/^-{1,2}/.test(flag) ? flag : '--' + flag));

示例代码

// node myScript.js -s --test --cool=true
hasFlags('-s'); // true
hasFlags('--test', 'cool=true', '-s'); // true
hasFlags('special'); // false

hashNode

Creates a hash for a value using the SHA-256 algorithm. Returns a promise.

Use crypto API to create a hash for the given value, setTimeout to prevent blocking on a long operation, and a Promise to give it a familiar interface.

const crypto = require('crypto');
const hashNode = val =>
  new Promise(resolve =>
    setTimeout(
      () =>
        resolve(
          crypto
            .createHash('sha256')
            .update(val)
            .digest('hex')
        ),
      0
    )
  );

示例代码

hashNode(JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })).then(console.log); // '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'

isDuplexStream

Checks if the given argument is a duplex (readable and writable) stream.

Check if the value is different from null, use typeof to check if a value is of type object and the pipe property is of type function. Additionally check if the typeof the _read, _write and _readableState, _writableState properties are function and object respectively.

const isDuplexStream = val =>
  val !== null &&
  typeof val === 'object' &&
  typeof val.pipe === 'function' &&
  typeof val._read === 'function' &&
  typeof val._readableState === 'object' &&
  typeof val._write === 'function' &&
  typeof val._writableState === 'object';

示例代码

const Stream = require('stream');
isDuplexStream(new Stream.Duplex()); // true

isReadableStream

Checks if the given argument is a readable stream.

Check if the value is different from null, use typeof to check if the value is of type object and the pipe property is of type function. Additionally check if the typeof the _read and _readableState properties are function and object respectively.

const isReadableStream = val =>
  val !== null &&
  typeof val === 'object' &&
  typeof val.pipe === 'function' &&
  typeof val._read === 'function' &&
  typeof val._readableState === 'object';

示例代码

const fs = require('fs');
isReadableStream(fs.createReadStream('test.txt')); // true

isStream

Checks if the given argument is a stream.

Check if the value is different from null, use typeof to check if the value is of type object and the pipe property is of type function.

const isStream = val => val !== null && typeof val === 'object' && typeof val.pipe === 'function';

示例代码

const fs = require('fs');
isStream(fs.createReadStream('test.txt')); // true

Recommended Resource - JavaScript: The Hard Parts

Take your JavaScript to the next level. Gain an understanding of callbacks, higher order functions, closure, asynchronous and object-oriented JavaScript!

isTravisCI

Checks if the current environment is Travis CI.

Checks if the current environment has the TRAVIS and CI environment variables (reference).

const isTravisCI = () => 'TRAVIS' in process.env && 'CI' in process.env;

示例代码

isTravisCI(); // true (if code is running on Travis CI)

isWritableStream

Checks if the given argument is a writable stream.

Check if the value is different from null, use typeof to check if the value is of type object and the pipe property is of type function. Additionally check if the typeof the _write and _writableState properties are function and object respectively.

const isWritableStream = val =>
  val !== null &&
  typeof val === 'object' &&
  typeof val.pipe === 'function' &&
  typeof val._write === 'function' &&
  typeof val._writableState === 'object';

示例代码

const fs = require('fs');
isWritableStream(fs.createWriteStream('test.txt')); // true

JSONToFile

Writes a JSON object to a file.

Use fs.writeFile(), template literals and JSON.stringify() to write a json object to a .json file.

const fs = require('fs');
const JSONToFile = (obj, filename) =>
  fs.writeFile(`${filename}.json`, JSON.stringify(obj, null, 2));

示例代码

JSONToFile({ test: 'is passed' }, 'testJsonFile'); // writes the object to 'testJsonFile.json'

readFileLines

Returns an array of lines from the specified file.

Use readFileSync function in fs node package to create a Buffer from a file. convert buffer to string using toString(encoding) function. creating an array from contents of file by spliting file content line by line (each \n).

const fs = require('fs');
const readFileLines = filename =>
  fs
    .readFileSync(filename)
    .toString('UTF8')
    .split('\n');

示例代码

/*
contents of test.txt :
  line1
  line2
  line3
  ___________________________
*/
let arr = readFileLines('test.txt');
console.log(arr); // ['line1', 'line2', 'line3']

untildify

Converts a tilde path to an absolute path.

Use String.prototype.replace() with a regular expression and OS.homedir() to replace the ~ in the start of the path with the home directory.

const untildify = str => str.replace(/^~($|\/|\\)/, `${require('os').homedir()}$1`);

示例代码

untildify('~/node'); // '/Users/aUser/node'

UUIDGeneratorNode

Generates a UUID in Node.JS.

Use crypto API to generate a UUID, compliant with RFC4122 version 4.

const crypto = require('crypto');
const UUIDGeneratorNode = () =>
  ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
    (c ^ (crypto.randomBytes(1)[0] & (15 >> (c / 4)))).toString(16)
  );

示例代码

UUIDGeneratorNode(); // '79c7c136-60ee-40a2-beb2-856f1feabefc'