array note

const a = [1,2,3];
const b = a.concat();
console.log(b);
// [1,2,3]

let arrayLike = {
    ‘0‘: ‘a‘,
    ‘1‘: ‘b‘,
    ‘2‘: ‘c‘,
    length: 3
};

const arr = Array.from(arrayLike);
console.log(arr);
// [‘a‘,‘b‘,‘c‘]

// DOM 对象也是一个类数组对象
const ps = document.querySelectorAll(‘p‘);
const nodeList = Array.from(ps);

const arr = [1,2,3,1];
const newArr = new Set(arr);
console.log(newArr);
// [1,2,3]

// 无法对以下数组进行去重
const arr = [{id:1,name:‘a‘},{id:1,name:‘b‘}];

var arr = [1,2,3,4,5,6];
arr.some(item => (item > 3));
// true

var arr = [1,2,3,4,5,6];
arr.filter(item => (item > 3));
// [4,5,6]

const arr = [1,2,3,4];
arr.reduce((previousValue, currentValue, index, array) => {
	retrun previousValue + currentValue;
}, initialValue)
// 10

const arr = [1,2,3,4];
arr.map(item => item + 1);
// [2,3,4,5]

const arr = [1,2,3,4];
const newArr = [];
arr.forEach(item => newArr.push(item + 1))
console.log(newArr);
// [2,3,4,5]