function padLeft(value: string, padding: string | number) { if (isNumber(padding)) { return Array(padding + 1).join(" ") + value; } if (isString(padding)) { return padding + value; } throw new Error(`Expected s
But JavaScript was never meant for such large-scale application development. It is a dynamic language with no type system, meaning that a variable can have any type of value, such as a string or boolean. 但是,JavaScript从来都不适合进行如此大规模的应用程序开发。 这是一种没有类型系统的动态语言...
export function computeLineStarts(text: string): number[] { const result: number[] = new Array(); let pos = 0; let lineStart = 0; while (pos < text.length) { const ch = text.charCodeAt(pos); pos++; switch (ch) { case CharacterCodes.carriageReturn: if (text.charCodeAt(pos) ==...
function add(x:string,y:string):string; function add(x:number, y:number):number; // 报错,implementation没有实现该overload signatue function add(x:string, y: number|string): number | string{ if(typeof x === 'string'){ return x + ',' + y; }else { return 1; } } let x = ad...
string' is not assignable to 'string' index type 'number'.}然而，如果一个索引签名是属性类型的联合，那各种类型的属性就可以接受了：interface NumberOrStringDictionary { [index: string]: number | string; length: number; // ok, length is a number name: string; // ok, name is a string...
TypeScript 2.4 introduces the concept of “weak types”. Aweaktype is any type that contains nothing but all-optional properties. For example, thisOptionstype is a weak type: Copy interfaceOptions{ data?:string, timeout?:number, maxRetries?:number, ...
// @ts-check let obj = {}; Object.defineProperty(obj, "x", { value: "hello", writable: false }); obj.x.toLowercase(); // ~~~ // error: // Property 'toLowercase' does not exist on type 'string'. // Did you mean 'toLowerCase'? obj.x = "...
This type can be useful, but if a string has 50 leading spaces, you’ll get an error. Copy type TrimLeft<T extends string> = T extends ` ${infer Rest}` ? TrimLeft<Rest> : T; // error: Type instantiation is excessively deep and possibly infinite. type Test = TrimLeft<" oops">; ...
interfaceCanCheck{checkThing:(x:string|number)=>boolean;}constobj={checkThing:(s:string)=>{returntrue;}}objsatisfiesCanCheck;// Alleged: should be OK This is wrong. Ifobjis aCanCheck, thenobj.checkThing(42)is legal, and42would appear ins, which is only allowed to be astring. ...
(filename:string,options?:CreateReadStreamOptions)=>Stream.Readable optionsextendsmethod options. createWriteStream Create a write stream targeted at a remote file. Note that although a stream is returned instantly, the connection and writing to the remote file is still performed asynchronously in the...