今天分享几个少见却很有用的 JS 技巧

<button onclick="history.back()">
    返回
</button> 

const largeNumber = 1_000_000_000;

console.log(largeNumber); // 1000000000

element.addEventListener('click', () => console.log('I run only once'), {
    once: true
});        

const numbers = [6, 8, 1, 3, 9];

console.log(Math.max(...numbers)); // 9
console.log(Math.min(...numbers)); // 1  

const passwordInput = document.getElementById('password');

passwordInput.addEventListener('keyup', function (event) {
    if (event.getModifierState('CapsLock')) {
        // CapsLock 已经打开了
    }
});    

function copyToClipboard(text) {
    navigator.clipboard.writeText(text);
}     

document.addEventListener('mousemove', (e) => {
    console.log(`Mouse X: ${e.clientX}, Mouse Y: ${e.clientY}`);
});   

const numbers = [1, 2, 3, 4, 5]

numbers.length = 3;

console.log(numbers); // [1, 2, 3]   

// 普通写法
if (condition) {
    doSomething();
}

// 简写
condition && doSomething();   

// [] 里面指的是可选参数
console.table(data [, columns]);

// 一个对象数组，只打印 firstName
function Person(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
}

const john = new Person("John", "Smith");
const jane = new Person("Jane", "Doe");
const emily = new Person("Emily", "Jones");

console.table([john, jane, emily], ["firstName"]);

const numbers = [2, 3, 4, 4, 2];

console.log([...new Set(numbers)]); // [2, 3, 4]  

const str = '404';

console.log(+str) // 404;   

const myNumber = 403;

console.log(myNumber + ''); // '403'    

const myArray = [1, undefined, NaN, 2, null, '@denicmarko', true, 3, false];

console.log(myArray.filter(Boolean)); // [1, 2, "@denicmarko", true, 3]     

const myTech = 'JavaScript';
const techs = ['HTML', 'CSS', 'JavaScript'];

// 普通写法
if (myTech === 'HTML' || myTech === 'CSS' || myTech === 'JavaScript') {
    // do something
}

// includes 写法
if (techs.includes(myTech)) {
    // do something 
}           

const myArray = [10, 20, 30, 40];
const reducer = (total, currentValue) => total + currentValue;

console.log(myArray.reduce(reducer)); // 100     

<div id="user" data-name="John Doe" data-age="29" data-something="Some Data">
    John Doe
</div>

<script>
    const user = document.getElementById('user');
  
    console.log(user.dataset); 
    // { name: "John Doe", age: "29", something: "Some Data" }
  
    console.log(user.dataset.name); // "John Doe"
    console.log(user.dataset.age); // "29"
    console.log(user.dataset.something); // "Some Data"
</script>