プロのようにコーディングできるよう、20 以上の JavaScript ワンライナーを学習してください。

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

console.log(getRandomBoolean());
// a 50/50 chance of returning true or false

const isWeekend = (date) => [0, 6].indexOf(date.getDay()) !== -1;

console.log(isWeekend(new Date(2021, 4, 14)));
// false (Friday)
console.log(isWeekend(new Date(2021, 4, 15)));
// true (Saturday)

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

console.log(isEven(5));
// false
console.log(isEven(4));
// true

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

console.log(uniqueArr([1, 2, 3, 1, 2, 3, 4, 5]));
// [1, 2, 3, 4, 5]

const isArray = (arr) => Array.isArray(arr);

console.log(isArray([1, 2, 3]));
// true
console.log(isArray({ name: 'Ovi' }));
// false
console.log(isArray('Hello World'));
// false

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

console.log(random(1, 50));
// could be anything from 1 - 50

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

console.log(randomString());
// could be anything!!!

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

scrollToTop();

// bool is stored somewhere in the upperscope
const toggleBool = () => (bool = !bool);
//or
const toggleBool = b => !b;

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

const daysDiff = (date, date2) => Math.ceil(Math.abs(date - date2) / 86400000);

console.log(daysDiff(new Date('2021-05-10'), new Date('2021-11-25')));
// 199

const copyTextToClipboard = async (text) => {
  await navigator.clipboard.writeText(text);
};

// Merge but don't remove the duplications
const merge = (a, b) => a.concat(b);
// Or
const merge = (a, b) => [...a, ...b];

// Merge and remove the duplications
const merge = [...new Set(a.concat(b))];
// Or
const merge = [...new Set([...a, ...b])];

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

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

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

console.log(
  truncateString(&#39;Hi, I should be truncated because I am too loooong!&#39;, 36),
);
// Hi, I should be truncated because...

const truncateStringMiddle = (string, length, start, end) => {
  return `${string.slice(0, start)}...${string.slice(string.length - end)}`;
};

console.log(
  truncateStringMiddle(
    'A long story goes here but then eventually ends!', // string
    25, // 需要的字符串大小
    13, // 从原始字符串第几位开始截取
    17, // 从原始字符串第几位停止截取
  ),
);
// A long story ... eventually ends!

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

console.log(capitalize('hello world'));
// Hello world

const isTabInView = () => !document.hidden;  // Not hidden

isTabInView();
// true/false

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

console.log(isAppleDevice);
// true/false

// Longhand
const age = 18;
let greetings;

if (age < 18) {
  greetings = &#39;You are not old enough&#39;;
} else {
  greetings = &#39;You are young!&#39;;
}

// Shorthand
const greetings = age < 18 ? &#39;You are not old enough&#39; : &#39;You are young!&#39;;

// Longhand
if (name !== null || name !== undefined || name !== '') {
  let fullName = name;
}

// Shorthand
const fullName = name || 'buddy';