如何改进错误的 str 检查？

Question

I have a varaible:

public searchValue: string;

And conditions that checks if variable is not empty:

const searchQuery = this.searchValue && 
  this.searchValue.toString().trim().length ? 
    `appname[like]${this.searchValue.toString().trim()}` : 
    null;

if (!searchQuery) return;

How to improve this if ?

Answer 1

searchValue is a string, so it doesn't have a .toString() method:) Just check for:

typeof searchValue === "string" && searchValue.trim().length;

Answer 2

Shorter and easier to read

I am using optional chaining to not get an error when trying to trim null/undefined

const val = this.searchValue?.trim();
const searchQuery = val.length ? `appname[like]${val}` : null;
if (!searchQuery) return; // note: return needs to be in a function