Type 'null' is not assignable to type 'HTMLInputElement' 请让我知道这里到底有什么不正确的地方,我使用了来自 React https://reactjs.org/docs/refs-and-the-dom.html 的文档,但我认为我在这里做错了。以下是范围片段 class Results extends React.Component<{}, any> { private textInput: HTMLInputElem...
TypeScript Version: 3.0.1 Search Terms: null checks Type 'null' is not assignable Code interface Foo { prop?: boolean; } const bar: Foo = { prop: null }; I am not sure, if it's working as expected with TypeScript 3, but I didn't find any...
Version 2.5.16 Reproduction link Vue.component('union-prop', { props: { anything: null, primitive: [String, Number], object: [Cat, User], regex: RegExp, mixed: [RegExp, Array], union: [User, Number] as {new(): User | Number}[] // require...
Argument of type 'string | null' is not assignable to parameter of type 'string'. 代码: JSON.parse(sessionStorage.getItem("user") ).userId; 原因: sessionStorage.getItem("user") 方法可能返回null , 而null 不是字符串 ,则JSON.parse在执行时就会出错,...
letunusable:void=undefined;//okletunusable:void=null;//Type 'null' is not assignable to type 'void' 函数只要没有显性的返回值,ts推断后返回值的类型都是undefine; unctionf5():void{return; }constfv5 =f5(); console.log(fv5);//undefine ...
Typescript为javascript加入了众多类型声明语法，灵活使用可使代码变得健壮，不严谨的类型声明会带来后期的...
Type 'undefined' is not assignable to type 'string'. 要解决以上问题,我们可以加个条件判断: function handler (arg: string | null | undefined) { let str: string; if (arg) { str = arg; } // ... } 此外, 可以使用TypeScript2.0中提供的非空断言操作符(non-null-assertion-operator)。
// Type 'Boolean' is not assignable to type 'boolean'. // 'boolean' is a primitive, but 'Boolean' is a wrapper object. Prefer using 'boolean' when possible. 1. 2. 3. 4. 事实上 new Boolean() 返回的是一个 Boolean 对象: ...
letu:void;letnum: number = u;// Type 'void' is not assignable to type 'number'.letvo:void= u;// 编译通过 任意值Any 任意值(Any)用来表示允许赋值为任意类型。一个普通类型,在赋值过程中是不被允许改变类型的,any 类型,允许被赋值为任意类型。
// Type 'void' is not assignable to type 'number'. any 任意值(Any)用来表示允许赋值为任意类型。 如果是一个普通类型,在赋值过程中改变类型是不被允许的: let myFavoriteNumber: string = 'seven'; myFavoriteNumber = 7; // index.ts(2,1): error TS2322: Type 'number' is not assignable to ...