# typescript ###### tags: `教學` ---- ## javascript VS typescript - ### 靜態強型別 - ### javascript的超集 - ### 對於物件導向的支援更好 - ### 語法較為統一 - ### 減少debug所花費的時間 - ### 聰明的錯誤提示 --- ## tsconifg ```bash= yarn init -y yarn add -D typescript tsc init // yarn run tsc init ``` ---- 你或許會需要這個酷東西 ```bash= yarn add -D ts-node ``` --- # type ---- ## primitives type - string - number - boolean - undefined - null - symbol - void ---- ```typescript= let num1 = 1; let num2:number; num2 = 1; ``` ---- ## object type - Array \<T\> - JSON - class instance - tuple - map - enum ---- ```typescript= let arr1:Array<number> = [1,2,3] let arr2:number[] = [1,2,3] let obj={ attr1:123, attr2:'str' } let tuple :[number,string,obj] let map = new Map([ ["key1",1], ["key2",2] ]); enum msg{ susseces, error } ``` ---- ## 特殊型別 - any - nerver - unknow ---- ```typescript= let shit:any = 'str'; let obj:number; obj = shit; console.log(obj); ``` ----  ---- ## 複合型別 - | - & --- ## ?! ----  ---- ## const vs readonly | | const | readonly | | -------- | ----------------------- | ------------ | | 目的 | 避免重新賦值 | 避免重新賦值 | | 檢查時間 | run-time & compile-time | compile-time | | 目標 | variable | property | --- ## narrowing & type guard ---- - typeof - instanceof - in - is - ...