工作筆記: dz-01 4,5 兩個月的濃縮再濃縮 XDDD

開個新的 戰場

讓自己頭腦可以回顧溫習

工作上遇到的好玩事務~

eslint + auto fix vsc

• eslint: 快樂好文章
  • 安裝
    • npm install --global eslint
  • cd 到你要導入的開發環境下 root 位置
    • eslint --init
  • 都正常後會在root位置下幫你新增一個 eslintrc.json(我是選json格式)

• VSC 專案的 root 開一個 .vscode folder

  • 然後加入 settings.json

   {
       "editor.codeActionsOnSave": {
           "source.fixAll.eslint": true
         },
         "eslint.validate": ["javascript"]
   }
  

Go

Type Assertions

x.(T) asserts that x is not nil and that the value stored in x is og type T.

• ex:

   package main
        
   import "fmt"
   import "math"
        
   func main() {
       shapes := []Shape{
           Circle{1.0},
           Square{1.772453},
           Rectangle{5, 10},
           Triangle{10, 4, 7},
       }
       for _, v := range shapes {
           fmt.Println(v, "\tArea:", v.Area())
           if t, ok := v.(Triangle); ok {
               fmt.Println("Angles:", t.Angles())
           }
       }
   }
        
   type Shape interface {
       Area() float64
   }
   type Circle struct {
       Radius float64
   }
   type Triangle struct {
       A, B, C float64 // lengths of the sides of a triangle.
   }
   type Rectangle struct {
       A, B float64
   }
   type Square struct {
       A float64
   }
        
   func (t Circle) Area() float64 {
       return math.Pi * t.Radius * t.Radius
   }
        
   // Heron's Formula for the area of a triangle
   func (t Triangle) Area() float64 {
       p := (t.A + t.B + t.C) / 2.0 // perimeter half
       return math.Sqrt(p * (p - t.A) * (p - t.B) * (p - t.C))
   }
   func (t Rectangle) Area() float64 {
       return t.A * t.B
   }
        
   func (t Square) Area() float64 {
       return t.A * t.A
   }
        
   func (t Circle) String() string {
       return fmt.Sprint("Circle (Radius: ", t.Radius, ")")
   }
   func (t Triangle) String() string {
       return fmt.Sprint("Triangle (Sides: ", t.A, ", ", t.B, ", ", t.C, ")")
   }
   func (t Rectangle) String() string {
       return fmt.Sprint("Rectangle (Sides: ", t.A, ", ", t.B, ")")
   }
   func (t Square) String() string {
       return fmt.Sprint("Square (Sides: ", t.A, ")")
   }
        
   func (t Triangle) Angles() []float64 {
       return []float64{angle(t.B, t.C, t.A), angle(t.A, t.C, t.B), angle(t.A, t.B, t.C)}
   }
   func angle(a, b, c float64) float64 {
       return math.Acos((a*a+b*b-c*c)/(2*a*b)) * 180.0 / math.Pi
   }
  

• reference:

  • Type assertions
  • How to convert interface{} to string?
  • Explain Type Assertions in Go

---

cap vs len

• cap tells you the capacity of the underlying array

• len tells you how many items are in the array

• ex:

   s := make([]int, 0, 3)
   for i := 0; i < 5; i++ {
       s = append(s, i)
       fmt.Printf("cap %v, len %v, %p\n", cap(s), len(s), s)
   }
  

   cap 3, len 1, 0x1040e130
   cap 3, len 2, 0x1040e130
   cap 3, len 3, 0x1040e130
   cap 8, len 4, 0x10432220
   cap 8, len 5, 0x10432220
  

• reference:

  • cap vs len of slice in golang

---

xrom inner join 用法

JavaScript

reduce MDN: reduce()

~~~js
let input = [{id: 1, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2019-12-15T00:00:00", year: 2019, month: "December"},
{id: 2, companyName: "company5", companyId: 5, flActive: true, purchaseMonth: "2019-12-15T00:00:00", year: 2019, month: "December"},
{id: 3, companyName: "company13", companyId: 13, flActive: true, purchaseMonth: "2019-11-15T00:00:00", year: 2019, month: "November"},
{id: 4, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2019-11-15T00:00:00", year: 2019, month: "December"},
{id: 5, companyName: "company5", companyId: 5, flActive: true, purchaseMonth: "2019-10-15T00:00:00", year: 2019, month: "October"},
{id: 6, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2020-09-15T00:00:00", year: 2020, month: "September"},
{id: 7, companyName: "company7", companyId: 7, flActive: true, purchaseMonth: "2020-09-15T00:00:00", year: 2020, month: "September"}]

let months = { "09": "September", "10": "October", "11": "November", "12": "December" }

let result = input.reduce((state,current) => {
   let {companyName, year, month} = current;
   
   let company = state[companyName] || (state[companyName] = {});
   let yearObj = company[year] || (company[year] = {});
   let monthArr = yearObj[month] || (yearObj[month] = []);
   monthArr.push(current);
   
   return state;
}, {});

console.log(result);
~~~

---

React

route with path params

• 在Route 中的寫法

   <Route  exact path="/pathName/:id" component={ Wooh }/>
  

• 在 components 拿 path params
  • 招數一

       const Wooh = ({match}) => {
              return (
                <div>
              id: {match.params.id}
            </div>
          )
       }
    

  • 招數二

      import { useParams } from "react-router";
      　const Wooh = () => {
             let {id} = useParams()
      　   return (
       　　     <div>
      　       id: {id}
      　     </div>
      　   )
    

• reference