When looking at large numbers in code (such as 1800000) it’s oftentimes difficult for the human eye to quickly see how big the number actually is. TypeScript allows us to use numeric separators to write numbers in a more human readable format (such as 1_800_000), while keeping the generated JavaScript unchanged.
Since Typescript 1.7, we are able to do:
const num: number = 123_456_789; // the same as 123456789
There is no limit how you add _ to the number, just make it reasonable.
[Typescript] Improve Readability with TypeScript Numeric Separators when working with Large Numbers
原文：https://www.cnblogs.com/Answer1215/p/10267710.html