JavaScript Reflection with toString

Reflection is an important tool in programming; it lets us examine a language’s structure. Can we reflect in JavaScript? Sort of.

Some functions can be reflected with toString():

> const one = () => 1
undefined
> one.toString()
'() => 1'

Very cool! But native functions only return this:

> Math.max.toString()
'function max() { [native code] }'

You must read the ECMA Script specification to know what the function is required to do. The actual implementation is written in the JavaScript engine, likely in another language like C++, which is why Node can’t show it via toString().