We want the union type. We want to loop. But as far as I can tell, looping requires code. We need an iterable, like an array. We can't loop through the type per se. So let's first create the array in code, then derive the type from it: ...
In TypeScript, we can use the for-loops to iterate through the iterable objects such asarray,map,set,string,arguments objectand so on. This article explores the TypeScriptfor-loop, and its syntax, providing code examples, and explaining its various components. TypeScript supports 3 types of f...
roArray = yy; // 因为const定义的。❌类型 "readonly string[]" 为 "readonly",不能分配给可变类型 "string[]" yy = roArray; // ❌类型 "readonly string[]" 为 "readonly",不能分配给可变类型 "string[]"。 函数 js 的一等公民,使用场景太多了 函数:支持给参数、返回值定义类型;默认参数...
interfacePadder{getPaddingString():string;}classSpaceRepeatingPadderimplementsPadder{constructor(privatenumSpaces:number){}getPaddingString(){returnArray(this.numSpaces+1).join(" ");}}classStringPadderimplementsPadder{constructor(privatevalue:string){}getPaddingString(){returnthis.value;}}letpadder:Padder=...
function error(message: string): never { throw new Error(message); } function infiniteLoop(): never { while (true) {} }在TypeScript 中,可以利用 never 类型的特性来实现全面性检查,具体示例如下:type Foo = string | number; function controlFlowAnalysisWithNever(foo: Foo) { if (typeof foo =...
{ const loop = (data: TreeDataNode[]): TreeDataNode[] => { return data.filter((item) => { const strTitle = String(item.title); const isMatch = strTitle.toLowerCase().includes(searchValue.toLowerCase()); const hasMatchingChildren = item.children && loop(item....
数组(Array) constarr1:Array<number> = [1,2,3]constarr2:number[] = [1,2,3] 元祖(Tuple) 元祖类型允许表示一个已知元素数量和类型的数组,各元素的类型不必相同。 constarr1: [number,string] = [100,'hello'] 空值(void) 某种程度上来说,void类型像是与any类型相反,它表示没有任何类型,当一个函...
strict' /* 额外的检查 */ "noUnusedLocals": true, // 有未使用的变量时,抛出错误 "noUnusedParameters": true, // 有未使用的参数时,抛出错误 "noImplicitReturns": true, // 并不是所有函数里的代码都有返回值时,抛出错误 "noFallthroughCasesInSwitch": true, // 报告 switch 语句的 fallthrough ...
String 类型let name: string = "Semliker";// ES5:var name = 'Semlinker';2.4 Array 类型let list: number[] = [1, 2, 3];// ES5:var list = [1,2,3];let list: Array<number> = [1, 2, 3]; // Array<number>泛型语法// ES5:var list = [1,2,3];...
}functioninfiniteLoop():never{while(true) {} } 在TypeScript 中,可以利用 never 类型的特性来实现全面性检查,具体示例如下: typeFoo=string|number;functioncontrolFlowAnalysisWithNever(foo: Foo) {if(typeoffoo ==="string") {// 这里 foo 被收窄为 string 类型}elseif(typeoffoo ==="number") {//...