Here we will see how to enum gets key by string value in typescript by using for…in loop. Thefor..in loopin typescript is used to loop through the properties of an object. Also, this is used to iterate over the
function getValueFromKey(obj: object, key: string) { // throw error // key的值为string代表它仅仅只被规定为字符串 // TS无法确定obj中是否存在对应的key return obj[key]; } 显然,我们直接为参数声明类型这是会报错的。同学们可以结合刚刚学过的 keyof 关键字配合泛型来思考一下如何消除 TS 的错误提示。
写一个get函数,输入对象和key,返回对应的value 代码语言:javascript 代码运行次数:0 运行 AI代码解释 // 这种时候,可能就开始写any了。因为不知道传入的是什么functiongetValue(o:any,k:string):any{returno[k]}getValue({a:1,b:'2'},'a');// 稍微好一点的可能是“觉得这是对象所以是object”// functi...
exporttype BasicPrimitive=number|string|boolean;exportfunctiondoStuff(value:BasicPrimitive){letx=value;returnx;} 如果我们在Visual Studio、Visual Studio Code 或 TypeScript Playground 之类的编辑器中将鼠标悬停在x上时,我们将得到一个快速信息面板,显示其类型为BasicPrimitive。同样,如果我们得到这个文件的声明文件...
[key: number]: number;/*** Shortest name: {@link InterfaceL1.(:FUNCTOR)}* Full name: {@link (InterfaceL1:interface).(:FUNCTOR)}** {@label FUNCTOR}*/(source: string, subString: string): boolean;/*** Shortest name: {@link InterfaceL1.(:CONSTRUCTOR)}* Full name: {@link (Interface...
import { createRpcBffLoader } from '@ctrip/rpc-bff-client' export type JsonType = | number | string | boolean | null | undefined | JsonType[] | { toJSON(): string } | { [key: string]: JsonType } /** * @label HelloInput ...
这是一个类型安全的解决方案,而不是简单地调用let value = obj[key];之类的东西。 从这里getProperty函数很容易调用,如下面的例子所示,从typescript_info对象中获取属性: // the property we will get will be of type Difficultyenum Difficulty { Easy, Intermediate, Hard}// defining the object we will ...
If we try to assign anything other than a boolean value, we’ll get an error. Copy interface BooleanDictionary { [key: string]: boolean; } declare let myDict: BooleanDictionary; // Valid to assign boolean values myDict["foo"] = true; myDict["bar"] = false; // Error, "oops" isn...
Add a Key Constraint toOmit Omits lack of key constraint is intentional. Many use cases for this type do not obey that constraint, e.g.: typeMySpread<T1,T2>=T2&Omit<T1,keyofT2>;typeX=MySpread<{a:string,b:number},{b:string,c:boolean}>;letx:X={a:"",b:"",c:true}; ...
are(x: number) => numberforfunctionsand{ x: number, y: number }for objects. If there is no certainty at all about the type,anyis the right choice, notObject. If the only known fact about the type is that it's some object, use the typeobject, notObjector{ [key: string]: any }...