TypeScript是一种由微软开发的开源编程语言,它是JavaScript的超集,为JavaScript添加了静态类型检查和其他一些特性。TypeScript 3.7引入了可选链操作符(optional chaining operator),它提供了一种简洁而安全的方式来访问深层嵌套的属性或方法,避免了在访问可能为null或undefined的属性时出现的错误。 要尝试TypeScript 3.7的可...
在TypeScript 中,有几个操作符在处理可能为null或undefined的值时非常有用,它们分别是可选链操作符(Optional Chaining Operator)、非空断言操作符(Non-null Assertion Operator)和空值合并操作符(Nullish Coalescing Operator)。下面是这些操作符的详细解释和示例: 1. 可选链操作符(Optional Chaining Operator) 可选链...
.operator which is known asoptional chaining. We're going to look at how we can use?.to safely descend into an object with properties which potentially hold the valuesnullorundefined. We're also going to learn how to access properties with an expression using the?.[]bracket notation and ho...
The star of the show in optional chaining is the new ?. operator for optional property accesses. When we write code like 代码语言:javascript 代码运行次数:0 运行 AI代码解释 let x = foo?.bar.baz(); this is a way of saying that when foo is defined, foo.bar.baz() will be computed;...
?? 空值合并运算符(Nullish coalescing Operator) ES12(ES2021)新增的特性,TypeScript 3.7 支持了这个特性,当左侧的操作数为null或者undefined时,返回其右侧操作数,否则返回左侧操作数。 // { // "level": null // } var level1 = user.level ?? '暂无等级' // level1 -> '暂无等级' ...
operator in TypeScript The question mark dot (?.) syntax is called optional chaining in TypeScript and is like using dot notation to access a nested property of an object, but instead of causing an error if the reference is nullish, it short-circuits returning undefined. index.ts type ...
At its core, optional chaining lets us write code where TypeScript can immediately stop running some expressions if we run into a null or undefined. The star of the show in optional chaining is the new ?. operator for optional property accesses. When we write code like let x = foo?.bar...
1. 可选链操作符(Optional Chaining Operator) 在TypeScript 4.4.3 中,引入了可选链操作符?.,它可以简化对可能为null或undefined的属性或方法的访问。下面是一个示例: classPerson{name:string;address?:{street:string;city:string;};}constperson:Person={name:'Alice',};constcity=person?.address?.city;con...
2.3 空值合并运算符(Nullish coalescing Operator) 当空值合并运算符的左表达式不为null或undefined时,不会对右表达式进行求值。 constgoods = {price:0, }letgoods1 = goods.price ??'暂无报价'letgoods2 = goods.jdPrice ??'暂无报价'console.log(goods1)//0console.log(goods2)//暂无报价 ...
2.4.2空值合并运算符(Nullish coalescing Operator) 空值合并运算符??是ES12(ES2021)新增的特性,TypeScript 3.7支持了这个特性。当左侧的操作数为null或者undefined时,返回其右侧操作数,否则返回左侧操作数。 与逻辑或操作符(||) 不同,||会在左侧操作数为falsy值(例如,''或0)时返回右侧操作数。也就是说,如果...