2. 非空断言操作符(Non-null Assertion Operator) 非空断言操作符!用于告诉 TypeScript 编译器某个值一定不是null或undefined。这在你确信某个值不为空但 TypeScript 无法推断出来的情况下非常有用。 注意: 滥用非空断言操作符可能会导致运行时错误,因此应谨慎使用。 示例: function getName(user: { name?: st...
You can use the non-null assertion operator in TypeScript to take a typed variable and remove theundefinedandnulltypes from it. In this lesson, we look at different ways to work around the null/undefined typed values; includingas [type]and the use of non-null assertion operator which is a...
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)。 语法 x! 非空断言操作符操作符 ! 可以用于断言操作对象是非 null 和非 undefined 类型。即: x! 将...
// Non-Null Assertion Operator const obj = null; interface Entity { name?: string; } // 非空断言操作符 function nonNull(e?: Entity) { const s = e!.name; // 发生断言,抛出TypeError } try { nonNull(obj); } catch (e) { console.error("nonNull catch", e); // TypeError: Cannot r...
Step 1: Enable the “strictNullChecks” Compiler Option Step 2: Use the Non-Null Assertion Operator (!) Step 3: Utilize Type Guards Step 4: Leverage the Nullable Type Pattern Conclusion Step 1: Enable the “strictNullChecks” Compiler Option ...
Non-null assertion operator(非空断言语句) Component type casting(组件类型重置) High order function for defining defaultProps(高阶组件) Props getter function(Getter函数) 1、 非空断言语句 1、constcolor =this.props.color!;2、this.props.onBlur ?this.props.onBlur(e): undefined; ...
)(Non-null Assertion Operator) TypeScript 提供了一个特殊的语法,可以在不做任何检查的情况下,从类型中移除 null 和undefined,这就是在任意表达式后面写上 ! ,这是一个有效的类型断言,表示它的值不可能是 null 或者undefined: function liveDangerously(x?: number | null) { // No error console.log(x!....
"@typescript-eslint/no-extra-non-null-assertion": "error" } } 选项 该规则无需配置额外选项。 正例 interface BarType1 { bar: number; } function getFoo(): BarType1 | null { return null; } const foo: BarType1 | null = getFoo(); export const bar1: number | undefined = foo?....
Error: Object is possibly ‘null’.ts(2531) However, if you use the non-null assertion operator, you can convey to the TypeScript compiler that the stringWord variable is never null or undefined. This is what the modified code looks like: let stringWord: string | null const number =1 ...
function doSomething(x: string | null) { if (x === null) { // do nothing } else { console.log("Hello, " + x.toUpperCase()); } } Non-null Assertion Operator (Suffix!) (Non-null Assertion Operator) TypeScript provides a special grammar that can removenullandundefinedfrom the type ...