about associativity and precedence.

• only right associativity
  • assignment a=b=5, same as a=(b=5)
  • exponentiation 幂运算， abc, same as a**(b**c)

window method

• alert

  • which was introdduced

    alert('the big one')
    

  • also (think why the difference between method alert and prompt, so this )

    console.log(alert('the big one'))
    // think why the difference between method alert and prompt, so this little try
    // but it runs, no mistake  
    

• prompt

  • introduced

    let number = prompt('Enter number', 'number goes here')
    console.log(number)
    

  • same changes

    let number = prompt('Enter number', )
    console.log(number);
    //it runs
    let number = prompt('Enter number', '')
    console.log(number);
    //it runs;
    let number = prompt('Enter number')
    console.log(number);
    //it runs; 
    

• confirm method

  const agree = confirm('Are you sure you like to delete? ')
  console.log(agree) // result will be true or false based on what you click on the dialog box
  

date object

const now = new Date()
console.log(now) // Sat Jan 04 2020 00:56:41 GMT+0200 (Eastern European Standard Time)

console.log(now.getFullYear()) // 2020

• about getTime

  const allSeconds = Date.now() //
  console.log(allSeconds) // 1578092201341, this is the number of seconds passed from January 1, 1970 to January 4, 2020 00:56:41
  
  const timeInSeconds = new Date().getTime()
  console.log(allSeconds == timeInSeconds) // true
  

review : string concatenation

• template string

  • the injection 直接包含在完整的string中，不需要把string断开之后又结合的操作

  console.log(`The sum of 2 and 3 is 5`)              // statically writing the data
  let a = 2
  let b = 3
  console.log(`The sum of ${a} and ${b} is ${a + b}`) // injecting the data dynamically
  //what is a problem is the symbol ```` , cannot be ''''
  //either would be a string when runs