•可空类型,默认任何类型都可以被赋值成 null 或 undefined。•联合类型,不确定类型是哪个,但能提供几种选择,如:type1 | type2。•交叉类型,必须满足多个类型的组合,如:type1 & type2。 类型都在哪里使用 在Typescript 中,类型通常在以下几种情况下使用。 •变量中使用•类中使用•接口中使用•函...
letuserList:string[] = ['John','Bob','Tony'];letpeopleList:object[] = [{name:'张三',age:18}]; Array<类型>写法, 如 letuser2List:Array<string> = ['John','Bob','Tony'];letpeople2List:Array<object> = [{name:'张三',age:18}]; 联合类型 组中既有 number 类型,又有 string 类型...
// "typeRoots": [], /* List of folders to include type definitions from. */ // "types": [], /* Type declaration files to be included in compilation. */ // "allowSyntheticDefaultImports": true, /* Allow default imports from modules with no default export. This does not affect code...
JavaScript 的类型分为两种:原始数据类型(Primitive data types)和对象类型(Object types)。原始数据类型包括:布尔值、数值、字符串、null、undefined 以及 ES6 中的新类型 Symbol。本节主要介绍前五种原始数据类型在 TypeScript 中的应用。javascript原始类型:布尔值、数值、字符串、null、undefined,为变量指定类型,且...
interface Goods {id: stringname: stringprice: stringimage: string}const goodsMap: Record<string, Goods> = {}const goodsList: Goods[] = awaitfetch('server.com/goods/list')goodsList.forEach(goods => {goodsMap[goods.name] = goods}) ...
letlist:Array<number> = [1,2,3]; There's no advantage to using one over the other, so it's up to you to decide which syntax to use. Tuples Having an array of the same value types is useful, but sometimes you have an array that contains values of mixed types. For that purpose...
Here’s a quick list of what’s new in TypeScript 4.8! Improved Intersection Reduction, Union Compatibility, and Narrowing Improved Inference for infer Types in Template String Types --build, --watch, and --incremental Performance Improvements Errors When Comparing Object and Array Literals Improved...
Here’s a quick list of what’s new in TypeScript 5.1! Easier Implicit Returns for undefined-Returning Functions Unrelated Types for Getters and Setters Decoupled Type-Checking Between JSX Elements and JSX Tag Types Namespaced JSX Attributes typeRoots Are Consulted In Module Resolution Linked Curso...
console.log(list, typeof list); console.log(list2, typeof list2); console.log(list3, typeof list3); 其中list 就是使用了type[]这样的声明方式,声明为number[],那么数组里面的每个元素都必须要是 number 类型,list2 则是使用了泛型类型的声明,和 list 的效果是一样的,另外 list3 使用了 any泛型...
const valueList = [123, "abc"]; const getRandomValue = () => { const number = Math.random() * 10; // 这里取一个[0, 10)范围内的随机值 if (number < 5) { return valueList[0]; // 如果随机数小于5则返回valueList里的第一个值,也就是123 }else { return valueList[1]; // 否则...