Javascript 기초-1

0. 출력

console.log()

 

1. String

string0 = "like this"
string1 = "this is a string"
string2 = 'single quotes and double quotes are equivalent'
string3 = `using backticks allow you to set arguments ${string0}`         # template literal

 

2. const (boolean, integer, float)

const number = 999
const negative = -999
const fraction = .250
const b = true

 

3. let (dynamic typing)

let age                                # implicit declaration -> age doesnt exist
let age = undefined            # same as above
let age = null                      # explicit declaration -> age not defined yet

 

4. Array

const fruits = new Array('apple', 'banana', 'cherry')
const fruits = ['apple', 'banana', 'cherry']
console.log(fruits)


console.log(fruits[1])                 # 'banana'
console.log(fruits.length)          # 3

 

5. 타입 분별법

console.log(typeof(fraction))                 # number
console.log(typeof fraction)                   # number

 

6. 자바스크립트상의 계산오류

const n1 = 0.1
const n2 = 0.2
console.log(n1 + n2)                            # 0.30000000000000004
console.log( (n1 + n2).toFixed(1) )          # 0.3 (string)

 

7. Type conversion 및 casting

console.log( (n1+n2).toFixed(1) )                     # 0.3 (string)
console.log( Number((n1+n2).toFixed(1)) )      # 0.3 (number)