JavaScript

值类型数据
let name = "hhh";
let age = 30;   //number类型
let isTure = false;
let firstName;  //undefined
let color = null;   //一般用于清空变量值

1.Object:{}表示对象；name:'Jone'表示key:value；多个key:value之间用,隔开
let person = {
    name:'Jone',
    age:'30'
}

2.修改变量
".":默认使用
person.name = 'Mary';


.[]:不知道属性时使用，由客户端来决定名字
let selection = 'name';
person[selection] = 'the Mike';

console.log(person.name);

Arrays:
let selectedColor = ['red','green'];
selectedColor[2] = 1;
console.log(selectedColor); //[ 'red', 'green', 1 ]
console.log(selectedColor[2]);  //1
console.log(selectedColor.length);  //3



//Function:Performance a task
function greet(name,lastName){
    console.log('hello,' + name + '  ' + lastName);
}
greet('abs','sdfj');

//or calculating a value
function calculating(number){
    return number * number;
}
console.log(calculating(2));

let a = 2;
let c = 3;

//算数运算符：加减乘除、取余、++、--、+=(其它同理)、
//取幂
console.log(a ** c);

//比较运算符
let x = 1;

//比较
// console.log(x > 2);
// console.log(x === 1);
// console.log(x !== 1);

// Strict Equality (Type + Value)
console.log(1 === 1);   //true
console.log('1' === 1); //false

// Lose Equality 会自动将右边转化为左边的格式
console.log(1 == 1);    //tuue
console.log('1' == 1);  //tuue
console.log(true == 1); //tuue

//三元运算符
let points = 110;
let type = points > 100 ? 'gold':' silver';
console.log(type);

//逻辑运算符：&&、||、！
// let userColor = 'red';
let userColor = undefined;
let defaultColor = 'blue';
let currentColor = userColor || defaultColor;

console.log(currentColor);

//位元或运算：添加权限
//位元与运算：检测是否拥有权限

逻辑运算符

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位运算符（位元或运算：添加权限；位元与运算：检测是否拥有权限）

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