Primative

A primitive (primitive value, primitive data type) is data that is not an object and has no methods.

Primitive is immutable, stored by value

1. String
2. Number
3. Boolean
4. Null
5. Undefined
6. Symbol
7. BigInt

Primitive Wrapper

Object type is stored by reference(in heap memory)

1. Object
2. Function
3. Array
4. Set

Check isArray

function isArrayFn(obj) {
  // 包成函式
  if (typeof Array.isArray === 'function') {
    return Array.isArray(obj) // 如果瀏覽器支援就用 isArray() 方法
  } else {
    // 否則就使用 toString 方法
    return Object.prototype.toString.call(obj) === '[object Array]'
  }
}