• Find function return the first element in an array that fits the certain condition.
• Filter function works like find, but will return all the things that fit the condition.(in an array)
• 跟map一樣需要callback function 、 需要 return
• 若找不到符合條件element，find() 會回傳 undifined；filter() 會回傳空陣列 [ ]

const record = [
  {name: "math", score: 89},
  {name: "chinese", score: 72},
  {name: "english", score: 91},
  {name: "science", score: 88}
];

let result1 = record.find(i => {
  return i.score > 80;
})

let result2 = record.filter(i => {
  return i.score > 80;
})

console.log(result1); // { name: 'math', score: 89 }
console.log(result2); // [ { name: 'math', score: 89 },{ name: 'english', score: 91 },{ name: 'science', score: 88 } ]

▲可以看到find只找到第一個符合條件的element，filter則是將所有符合元素組合成一個array