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JavaScript

in​

  • 如果指定的属性在指定的对象或其原型链中，则 in 运算符返回 true
  • in 运算符
const car = { make: 'Honda', model: 'Accord', year: 1998 };

if ('make' in car) {
	console.log(car.make);
}

crypto.randomUUID​

let uuid = crypto.randomUUID();
console.log(uuid); // for example "36b8f84d-df4e-4d49-b662-bcde71a8764f"

Intl.DateTimeFormat​

  • Intl.DateTimeFormat 是根据语言来格式化日期和时间的对象的构造器
  • Intl.DateTimeFormat
const date = new Date();

console.log(new Intl.DateTimeFormat('en-US').format(date)); // expected output: '12/17/2021'
console.log(new Intl.DateTimeFormat('zh-CN').format(new D())); // expected output: '2021/12/17'

Array.prototype.at​

  • Array.prototype.at 方法采用整数值并返回该索引处的元素，允许负数索引
  • Array.prototype.at
const list = [5, 12, 8, 130, 44];

console.log(list.at(-1)); // 44
console.log(list.at(-2)); // 130
console.log(list.at(0)); // 5

structuredClone​

  • structuredClone 使用结构化克隆算法创建一个给定值的深度克隆
  • structuredClone
const original = { name: 'MDN' };
original.itself = original;

// Clone it
const clone = structuredClone(original);

console.assert(clone !== original); // the objects are not the same (not same identity)
console.assert(clone.name === 'MDN'); // they do have the same values
console.assert(clone.itself === clone); // and the circular reference is preserved

Intl.NumberFormat​

  • Intl.NumberFormat 是对语言敏感的格式化数字类的构造器类
  • Intl.NumberFormat
new Intl.NumberFormat().format(123456); //'123,456'
new Intl.NumberFormat('zh-CN', { style: 'currency', currency: 'CNY' }).format(
	123456,
); // '¥123,456.00'