js 中实现getter和setter函数方法，及运算符的特…

const student = {
    firstName: 'job',
    lastName: 'jark',

    get fullName() {
        return this.firstName + ' ' + this.lastName;
    },

    set age(value) {
        if (isNaN(value)) throw Error("It has been a bumber");
        this_age = Number(value)
    },
    get age() {
        return this_age
    }
};
console.log(student.firstName);
student.firstName = 'jerry';
console.log(student.fullName);
student.age = '21';
console.log(student.age);
student.age = 'error';

var a,b,n = 6;
for(a = 0,b = 0;a <= n&&b<=n;a++,b++) {
}

function  calculate() {
    return a++,console.log(a),a;
}

let result = number1,number2,...,numberN;

!!null         //returns false
!!undefined   //returns false
!!false        //returns false
!!true         //returns true 
!!""           //returns false
!!"somestring" //returns true
!!0        //returns false
!!1        //returns true
!![]        //returns true
!!{}        //returns true

+ '3.11'     //returns 3.11
+ '-4'        //returns -4
+ '0xFF'      //returns 255
+ true        //returns 1
+ '123e-5'   //returns 0.00123
+ false      //returns 0
+ null        //returns 0
+ 'Infinity' //returns Infinity
+'1,234'     //returns Nan
+dateObject   //returns 1542975502981
+momentObject //returns 1542975502981

let userName = 'break jerry'

if(~userName.indexOf("break")) {
    console.log('access denied');
}else {
    console.log('access granted');
}