- Published on
Typescript 學習筆記 - Section 5
- Authors
-
-
- Name
- Alex Yu
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Section Overview
這章節主要會介紹如何使用 Typed Arrays
Arrays in Typescript
定義: 在 Typescript 的世界裡, array 裡面的 element 應該都維持一定程度上的相同型別
Examples
// typescript inference const carMakers: string[]
const carMakers = ['ford', 'toyata', 'chevy'];
// or typescript annotation
const carMakers: string[] = ['ford', 'toyata', 'chevy'];
const carMakers: string[] = [];
// typescript inference const carMakers: any[]
const carMakers = [];
// const dates: Date[]
const dates = [new Date(), new Date()];
// const carsByMake: string[][]
const carsByMake = [['f150'], ['corolla'], ['camaro']];Why Typed Array?
- Typescript(TS)可以幫助我們判斷從 array 取出來的值是什麼型別
- TS 可以幫助我們將錯誤型別的值加到 array 裡
- 當在使用 array.map, ‘forEach’, ‘reduce’的時候 TS 可以幫助我們判斷型別
- array 仍有一定的彈性加入不同型別的值
Examples
// Help with inference when extracting values
// const car: string
const car = carMakers[0];
// const myCar: string
const myCar = carMakers.pop();
// Prevent incompatible values
// get ts lint error
carMakes.push(100);
// Help with 'map'
carMakes.map((car: string): string => {
// get methods belongs to string
return car;
});Multiple Types in Arrays
// Flexible types
const importantDates: (Date | string)[] = [new Date()];
importantDates.push('2030-10-10');
importantDates.push(new Date());
// get ts lint error
importantDates.push(100);When to Use Typed Arrays
Anytime~