so basically null value means a variable has been explicitly set as (no value = null) or has been initialized and defined to be nothing. While undefined means. ... <看更多>

JavaScript null 、undefined 與undeclared · 宣告了，但是還沒有賦值. var a = undefined; console. · 物件沒有該屬性. var person = { name: "elaine", }; ... ... <看更多>

JavaScript (and by extension TypeScript) has two bottom types : null and undefined . They are intended to mean different things:. ... <看更多>

This tutorial introduces you to the JavaScript data types including primitive types that consist of undefined, null string, boolean, number, and symbol. ... <看更多>