How do I check for the existence of a variable

This question already has an answer here:

JavaScript check if variable exists (is defined/initialized) 28 answers

---

Just use typeof :

console.log(typeof FooClass) // undefined
console.log(typeof FooClass === 'undefined') // true

I doubt there's any need to use language features specific to TypeScript.

链接地址: http://www.djcxy.com/p/95014.html

上一篇: JavaScript检查变量是否存在（已定义/初始化）

下一篇: 我如何检查变量的存在