Question

For instance, open up a JS console, and type toString<Enter>.

You’ll get this:

function toString() { [native code] }

Contrast this with:

function foo() { return 'bar'; }
foo

which produces:

function foo() { return 'bar'; }

Does it mean that its an API to the interpreter which directly executes some internal routines in C or whatever is used to program it when that method is called?

Answer 1

[native code] is simply a label that indicates that the implementation details of the function body are handled “natively” by the browser.