JAVASCRIPT筆記 - Object

Object，Python上應該是dictionary跟它比較類似，或是Hash table

通常會包含key跟value，key不能重複，value則無規定

value可為string或number

寫法

let obj1 = {
  name: "Jack",
  gender:  "Male",
  birthday: "1992/3/4"
}

let group =   [
  { name: "Jack",   gender:  "Male",   birthday: "1992/3/4" },
  {name: "Mary",   gender:  "Female",   birthday: "1998/7/21" }
]

Object.value() =>輸出key對應的值

console.log(Object.values(obj1))
//"Jack", "Male" , "1992/3/4"

const obj2 = { 100: "hi", 2: "hello", 5: "bye" };
console.log(Object.values(obj2)); // ['hello', 'by', 'hi']
//key為數字時，會依照數字order回傳

Object.key() => 輸出key的值

console.log(Object.keys(obj1))
// ['name',   'gender' ,   'birthday']

console.log(Object.keys(obj2))
//[ '2', '5', '100']

Object.entries() =>同時輸出key跟value

也可以用迴圈

console.log(Object.entries(obj1))
// [ ["name", "Jack"], [ "gender", "Male"] , [ "birthday",  "1992/3/4"] ]

console.log(Object.keys(obj2))
//[ ['2', 'hello'] , [ '5', 'bye'], [100', hi]  ]

//forEach
Object.entries(obj1).forEach(([key, value]) => {
  console.log(`${key} ${value}`)
})
 // "name Jack",  "gender Male" , "birthday 1992/3/4"

//for...of
for (const [key, value] of Object.entries(obj1)) {
  console.log(`${key} ${value}`)
}
 // "name Jack",  "gender Male" , "birthday 1992/3/4"