for...of:迭代可迭代的对象,允许遍历 Arrays(数组), Strings(字符串), Maps(映射), Sets(集合)等可迭代的数据结构等;遍历的是value值; 例如: let s = [1,"string",false]; for(let e of s){ console.log(e); } 4)、forEach循环在 iteration 中是无法返回的 例: let list = [4,5,6]; list...
// covariance is not type safe animalList = catList; animalList.push(dog); catList.forEach(cat => cat.meow()); // cat.meow is not a function // contravariance is also not type safe, if it exist here catList = animalList; animalList.push(dog); catList.forEach(cat => cat.meow...
classMenu {//Our properties://By default they are public, but can also be private or protected.items: Array<string>;//The items in the menu, an array of strings.pages: number;//How many pages will the menu be, a number.//A straightforward constructor.constructor(item_list: Array<string...
let name: string = "Semliker";Array 类型 let list: number[] = [1, 2, 3];<T>泛型 let list: Array<T> = [1, 2, 3];any类型: 任意值,是 TypeScript 针对编程时类型不明确的变量使用的一种数据类型 let x: any = 1; // 数字类型x = 'I am who I am'; // 字符串类型x = false;...
setItemis defined as having the type(items: string[]) => void. This definition means it is a function that accepts an array of strings, for examplesetItem(['a', 'b', 'c'])would be a valid invocation of a function with this type. ...
1097 错误 '{0}' list cannot be empty. “{0}”列表不能为空。 1098 错误 Type parameter list cannot be empty. 类型参数列表不能为空。 1099 错误 Type argument list cannot be empty. 类型参数列表不能为空。 1100 错误 Invalid use of '{0}' in strict mode. 严格模式下“{0}”的使用无效。
gender:'女'}for(let keyValueinobjectList){ console.log(keyValue+':'+objectList[keyValue]) } 打印结果 name:小白狼 age:27 gender:女 for...of... 允许你遍历 Arrays(数组), Strings(字符串), Maps(映射), Sets(集合)等可迭代的数据结构等 ...
By default, TypeScript infers ananytype for any variable that has neither a declared type nor enough context to infer a type. To disable that, use thenoImplicitAnyor--strictTypeScript compiler flag. You can refer to the full list ofTypeScript compiler options. ...
items:Array<string>;// The items in the menu, an array of strings. pages:number;// How many pages will the menu be, a number. // A straightforward constructor. constructor(item_list:Array<string>,total_pages:number){ // The this keyword is mandatory. ...
list.push(null); // ✅ list.push('nope'); // ❌ - type 'string' is neither of type 'number' or 'null' 在上面的例子中,数组(list)是由number或null类型组成的,因此TypeScript只希望number或null类型的值加入数组。 类型注释 当类型推断系统不够用的时,你需要在变量和对象上声明类型。