[TypeScript ] Using the Null Coalescing operator with TypeScript 3.7
The postshows you how to use the null coalescing operator (??) instead of logical or (||) to set default values in TypeScript 3.7 to prevent expected bugs in your code.
const val = ;
const correct = (val !== undefined && val !== null) ? val : 0.5;
// const incorrect = val || 0.5; // || check all the falsy value
const incorrect = val ?? 0.5; // ?? check only null and undefined
console.log({ correct, incorrect });
[TypeScript ] Using the Null Coalescing operator with TypeScript 3.7的更多相关文章
- Null Coalescing Operator
w Parse error: syntax error, unexpected '?'
- js Nullish Coalescing Operator
js Nullish Coalescing Operator 空值合并 const n = null ?? 'default string'; console.log(n); // "def ...
- nil coalescing operator
nil coalescing operator ?? 就是 optional和 三元运算符?:的简写形式. 比如一个optional String类型的变量 var a:String? // prin ...
- [TypeScript] Use the JavaScript “in” operator for automatic type inference in TypeScript
Sometimes we might want to make a function more generic by having it accept a union of different typ ...
- [TypeScript] Define Custom Type Guard Functions in TypeScript
One aspect of control flow based type analysis is that the TypeScript compiler narrows the type of a ...
- [TypeScript] Distinguishing between types of Strings in TypeScript
In JavaScript, many libraries use string arguments to change behavior. In this lesson we learn how T ...
- [TypeScript] Union Types and Type Aliases in TypeScript
Sometimes we want our function arguments to be able to accept more than 1 type; e.g. a string or an ...
- [TypeScript] Using Assertion to Convert Types in TypeScript
Sometimes the compiler needs help figuring out a type. In this lesson we learn how to help out the c ...
- [TypeScript] Sharing Class Behavior with Inheritance in TypeScript
Typescript classes make inheritance much easier to write and understand. In this lesson we look into ...
随机推荐
- 栈习题(1)-对于任意的无符号的的十进制数m,写出将其转换为十六进制整数的算法(正确输出即可)
/*对于任意的无符号的的十进制数m,写出将其转换为十六进制整数的算法(正确输出即可)*/ /* 算法思想:利用辗转取余法,每次都将余数存入栈中,直到被除数等0,退出循环. 输出栈里的内容即可 */ v ...
- Django视图扩展类
Django视图扩展类 扩展类必须配合GenericAPIView使用扩展类内部的方法,在调用序列化器时,都是使用get_serializer 需要自定义get.post等请求方法,内部实现调用扩展类 ...
- machine learning相关会议
1. ICML(International Conference on Machine Learning) 链接:https://en.wikipedia.org/wiki/Internation ...
- iOS核心动画(专用图层篇)
之前的文章我们了解了Core Animation中图层的一些基础知识.没有看过的传送门在此: iOS核心动画基础篇 那么在了解了这些基础知识之后,接下来进入专用图层的了解 苹果为了方便和性能,封装了几 ...
- 排Bug技巧
排Bug技巧 什么是Bug? Bug一词的英文原意是"臭虫"或"虫子".但是现在,在电脑系统或游戏程序中,如果隐藏着的一些未被发现的缺陷或问题,可被人利用,人们 ...
- scrapy爬取相似页面及回调爬取问题(以慕课网为例)
以爬取慕课网数据为例 慕课网的数据很简单,就是通过get方式获取的 连接地址为https://www.imooc.com/course/list?page=2 根据page参数来分页
- python 多进程和协程配合使用
一.需求分析 有一批key已经写入到3个txt文件中,每一个txt文件有30万行记录.现在需要读取这些txt文件,判断key是否在数据仓库中.(redis或者mysql) 为空的记录,需要写入到日志文 ...
- 最清晰易懂的Mysql CURRENT_TIMESTAMP和ON UPDATE CURRENT_TIMESTAMP区别
timestamp数据类型 Mysql数据库中,当字段类型为timestamp(时间戳)时,如果默认值取CURRENT_TIMESTAMP,则在insert一条记录时,此时的值自动设置为系统当前时间, ...
- ppt thinkcell-Thinkcell: 一款强大的专业图表制作工具
https://jingyan.baidu.com/article/6dad50750e6121a123e36e00.html
- Java线程读写锁
排他锁和共享锁: 读写锁:既是排他锁,又是共享锁.读锁,共享锁,写锁:排他锁 读和读是不互斥的 import java.util.HashMap; import java.util.Map; impo ...