JavaScript笔记：基础知识

var str = ‘Hello World‘;

str[5] = ‘.‘;
var len = str.length;
var upperStr = str.toUpperCase();
var lowerStr = str.toLowerCase();
var i = str.indexOf(‘World‘);
var substr = str.substring(6, 11);

var arr = [0, 1.0, ‘1‘, true, undefined, null, []];

var len = arr.length;
var element = arr.indexOf(0);
var subArr = arr.slice(0, 5);

//向末尾添加元素或删除元素
arr.push(1, 2, 3);
arr.pop();

//向头部添加元素或删除元素
arr.unshift(4, 5, 6);
arr.shift();

var delArr = arr.splice(0, 3, ‘7‘, ‘8‘, ‘9‘); //删除内容后插入
arr.concat(delArr); //连接数组
var str = arr.join(‘-‘); //使用指定字符串连接

arr.sort();
arr.reverse();

var Player = {
    number: 30,
    name: ‘Stephen Curry‘,
    team: ‘Golden State Warriors‘,
};

Player[‘number‘]; //访问属性
Player.position = "Point Guard"; //添加属性
delete Player.position; //删除属性
‘positon‘ in Player; //判断属性是否拥有
Player.hasOwnProperty(‘position‘); //判断属性是否自身拥有

var arr = [];
for (var i = 0; i < 10; i++)
    arr.push(i);

var sum = 0;
for (var j in arr)
    if (j % 2 === 0)
        sum += parseInt(j);
alert(sum);

var arr = [0, 1, 2, 3, 4];
arr.name = "MyArray";

var str = ‘‘;
for (var i of arr)
    str += i;
alert(str);

var map = new Map();
map.set(1, "Spring");
map.set(2, "Summer");
map.delete(1);

var set = new Set();
set.add("Autumn");
set.add("Winter");
set.delete("Autumn");