kaka

const c = (x) => console.log(x);

// Declare a variable named challenge and assign it to an initial value '30 Days Of JavaScript'
let cha = "30 Days Of JavaScript";

// What is the character code of J in '30 Days Of JavaScript' string using charCodeAt()
const index = cha.indexOf("J");
c(cha.charCodeAt(index));


//Check if typeof '10' is exactly equal to 10. If not make it exactly equal.
c(typeof('10'));
c(parseInt('10'));

//Check if parseFloat('9.8') is equal to 10 if not make it exactly equal with 10.
c(parseFloat('9.8'));
c(Math.round(parseFloat('9.8')));

//Access the 'JavaScript' string characters using a random number.
c("JavaScript"[Math.round(Math.random() * 10)]);


//Use substr to slice out the phrase because because because from the following sentence:'You cannot end a sentence with because because because is a conjunction'
let phr = "You cannot end a sentence with because because because is a conjunction";
c(phr.indexOf("b"));
const length = "because because because".length;

c(phr.substr(31,length));

console.log(3 !== 3);

//Ternary Operators 看不懂


// Declare name, age, isMarried, year variable 
let name = "Xiaxia";
let age = 18;
let isMarried = true;
let year = 2020;
let fruits = ['apple', 'pear'];

// and assign value to it and use the typeof operator to check different data types.
c(typeof name);
c(typeof age);
c(typeof isMarried);
c(typeof year);
c(typeof fruits);

//Check if type of '10' is equal to 10
c(typeof '10' == 10);

//Check if parseInt('9.8') is equal to 10
c(parseInt('9.8') == 10);

//Boolean value is either true or false.
c(3 >= 3);
let truev = 4<3;
c(truev);

//Write three JavaScript statement which provide truthy value.


//Write three JavaScript statement which provide falsy value.

//Figure out the result of the following comparison expression first without using console.log(). After you decide the result confirm it using console.log()
c('>>>>>>>>>>>>>>>>>>>>>>>>>>>');
c(4 != '4'); // ?? false
c('>>>>>>>>>>>>>>>>>>>>>>>>>>>');

//There is no 'on' in both dragon and python
c("dragon" && "python".includes("on"));

//Use the Date object to do the following activities
//What is the year today?
let today = new Date();
c(today.getFullYear());

//What is the month today as a number?
c(parseInt(today.getMonth()));

//What is the date today?
c(today.getDate());

//What is the day today as a number?
c(parseInt(today.getDay()));

//What is the hours now?
c(today.getHours());

//What is the minutes now?
c(today.getMinutes());

//Find out the numbers of seconds elapsed from January 1, 1970 to now.
c(today.getTime());

c(Date.now());


// let height = prompt("enter height");
// height = parseInt(height);

// let input = prompt("enter demision, split by ','");
// const demision = input.split(',')
// const width = parseInt(demision[0]);
// const height = parseInt(demision[1]);

// const result = 0.5 * width * height
// document.querySeletor("#id").innerHTML = `<p>${result}</p>`;

// var checkNum = (num) => {
//   if (num > 10) {
//     c("big");
//   } 
//   else if (num > 5) {
//     c("medium");
//   } 
//   else if (num > 0) {
//     c("small");
//   } 
//   else {
//     c("negative");
//   }
// }

// == swtich

var checkNumber = (num) => {
  console.log(`num is ${num}`);
  switch (true) {
    case (num > 10): {
      console.log("10");
      // break;
    }
    case (num > 5): {
      console.log("5");
      // break;
    } 
    case (num > 0): {
      console.log("0");
      break;
    }
    
    default: {
      console.log("other");
    }
      
  }
}

checkNumber(20);


// var checkNum = (num) => {
//   if (num > 10) {
//     c("big");
//   } 
//   if (num > 5) {
//     c("medium");
//   } 
//   if (num > 0) {
//     c("small");
//   } 
//   else {
//     c("negative");
//   }
// }

var kaka1 = (num) => {
  if (num > 0) {
    console.log(">0")
  } else {
    console.log("<=0")
  }
}

var kaka2 = (num) => {
  num > 0 ? console.log(">0") : console.log("<=0")
}

var kaka3 = (num) => {
  const result = num > 0 ? ">0" : "<=0"
  console.log(result)
}

var kaka4 = (num) => {
  console.log(num > 0 ? ">0" : "<=0")
}

var kaka5 = (num) => {
  console.log(
    // the engineer has left. Do NOT touch the code! It just works and no one understands
    num > 10 ? 
      (num > 20 ? ">20" : ">10 <=20") : 
      (num < 5 ? "<5" : ">5 <=10")
  )
}


kaka5(16);

// checkNum(8);