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
解决方法:在遍历之前检查数组是否为空或未定义。 代码语言:txt 复制 function safeTraverseList(list: any[]): void { if (Array.isArray(list) && list.length > 0) { list.forEach((item) => { console.log(item); }); } else { console.log("数组为空或未定义"); } } 参考链接 ...
let x: number; let y: number; let z: number; let five_array = [0,1,2,3,4]; [x,y,z] = five_array; 8.2 数组展开运算符 let two_array = [0, 1]; let five_array = [...two_array, 2, 3, 4]; 8.3 数组遍历 let colors: string[] = ["red", "green", "blue"]; for (...
// Loop through each item in the original array arr.forEach((current, index) => { if (duplicatesIndices.includes(index)) return; result.push(current); // Loop through each other item on array after the current one for (let comparisonIndex = index + 1; comparisonIndex < arr.length; co...
2.5 Array 类型 2.6 Enum 类型 使用枚举我们可以定义一些带名字的常量。 使用枚举可以清晰地表达意图或创建一组有区别的用例。 TypeScript 支持数字的和基于字符串的枚举。 1.数字枚举 默认情况下,NORTH 的初始值为 0,其余的成员会从 1 开始自动增长。换句话说,Direction.SOUTH 的值为 1,Direction.EAST 的值为...
()method which we can call to try to get the next value as we iterate). By and large, you don’t typically have to think about these things when you toss them into afor/ofloop, or[...spread]them into a new array. But TypeScript does model these with the typesIterableandIterator(...
// 禁止使用 Array 构造函数,使用 Array(num) 直接创建长度为 num 的数组时可以 'no-array-constructor': 2, // 禁止将 await 写在循环里 'no-await-in-loop': 2, // 禁止位运算 // @off 不限制 'no-bitwise': 0, // 禁止在 Node.js 中直接调用 Buffer 构造函数 'no-buffer-constructor': 2,...
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 === "string") { ...
The queue uses the array push method to add a new callback function to the end of the queue and the array shift method to remove the first item in the queue.Callback functions will sit in the queue until the call stack is empty, they are then moved into the stack by the event loop...
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,当一个函数没有返回值...