functionprintValue(value:string|number):void{if(typeofvalue ==='string') {console.log(`The value is a string:${value}`);}elseif(typeofvalue ==='number') {console.log(`The value is a number:${value}`);}}classPerson {name:string;...
function printValue(value: string | number): void { if (typeof value === 'string') { console.log(`The value is a string: ${value}`); } else if (typeof value === 'number') { console.log(`The value is a number: ${value}`); } } class Person { name: string; constructor(na...
varfruitsArray:string[]=['apple','orange','lichi','banana'];if(fruitsArray.find(e=>e==='orange')){console.log('orange is present in array');} Output: "orange is present in array" Use thesome()Method to Check if a String Is Present in a TypeScript Array ...
AI代码解释 functionvalidateQuantity(target:any,propertyKey:string){letvalue=target[propertyKey];constgetter=function(){returnvalue;};constsetter=function(newValue:number){if(newValue<0){thrownewError("商品数量不能为负数。");}value=newValue;};Object.defineProperty(target,propertyKey,{get:getter,set:...
let strLength: number = (someValue as string).length; 四、类型守卫 A type guard is some expression that performs a runtime check that guarantees the type in some scope. —— TypeScript 官方文档 类型保护是可执行运行时检查的一种表达式,用于确保该类型在一定的范围内。换句话说,类型保护可以保证一...
{// 进行字段验证if(isValid(value)){originalValue=value;}else{thrownewError(`Invalid value for${propertyName}`);}},});}classForm{@validateFieldname:string;constructor(name:string){this.name=name;}}constform=newForm('John');form.name='Jane';// 合法的值form.name='';// 非法的值,会抛出...
letidentifier: number =value; 布尔类型:一个逻辑二进制开关,包含true或false letidentifier:string=" "; Null 类型: Null 表示值未定义的变量。 letidentifier:bool= Booleanvalue; 未定义类型:一个未定义的字面量,它是所有变量的起点。 letnum:number=null; ...
function isString(value: any): value is string { return typeof value === 'string'; } function compareIfStrings(a: any, b: any): boolean { if (isString(a) && isString(b)) { return a === b; } throw new Error("Both values must be strings"); ...
let myAdd: (baseValue: number, increment: number) => number = function(x: number, y: number): number { return x + y; }; 只要参数类型是匹配的,那么就认为它是有效的函数类型,而不在乎参数名是否正确。第二部分是返回值类型。对于返回值,我们在函数和返回值类型之前使用(=>)符号,使之清晰明了。
hasInstance](val: unknown): val is PointLike { return !!val && typeof val === "object" && "x" in val && "y" in val && typeof val.x === "number" && typeof val.y === "number"; } } function f(value: unknown) { if (value instanceof Point) { // Can access both of ...