ES14 2023 常用语法

// 1 新增Array方法
const numbers = [3, 1, 4];
let numbers1 = numbers.toSorted();
console.log('numbers1', numbers1);
let numbers2 = numbers.toSorted((a, b) => {
  return b - a;
});
console.log('numbers2', numbers2);
//toReversed()
let numbers3 = numbers1.toReversed();
console.log('numbers3', numbers3);
//toSpliced()
let numbers4 = numbers1.toSpliced(1, 2, 5, 6);
console.log('numbers4', numbers4);

//2 对WeakMap 支持使用Symbol作为键 在此之前是不支持的
const weakMap = new WeakMap();
let key = Symbol('key');
weakMap.set(key, 'value');
console.log('weakMap', weakMap.get(key));
//检查键是否存在
if (weakMap.has(key)) {
  console.log('包含key');
}
weakMap.delete(key);
console.log('hasKey', weakMap.has(key));
console.log(Symbol('a') === Symbol('a'));//false
console.log(Symbol.for('b') === Symbol.for('b'));//true

//3 Array.findLast() Array.findLastIndex()
const nums2 = [1, 2, 3, 4];
let num1 = nums2.findLast((n) => n > 1);
console.log('num1', num1);
let num2 = nums2.findLastIndex((n) => n > 1);
console.log('num2', num2);