This is a very old text, and I believe he is not referring to function closures (as I assume that you assume) but crazy shit like the long-since-deprecated-but-

This is a very old text, and I believe he is not referring to function closures (as I assume that you assume) but crazy shit like the long-since-deprecated-but-still-works arguments.callee.caller.arguments For example: function test() { console.log(arguments.callee.caller.arguments); } function test2(a, b) { test(); } test2('x', 2); Will print ['x', 2]. That is horrid; it makes it so you need to know the calling context to determine the behavior (and it could be globally anywhere; in a completely different .js file or even dynamically generated). With a closure the context of a function can generally be determined by simple static code inspection.