Why does console.log(this) in node return an empty object?

Question

When I ran console.log(this) in node it returns empty object

console.log(this)             // return { }

But when I used IIFE in node

(function printThisObject(){
   console.log(this);         // return the global object
})();

Can someone explain this to me ?

Related: How does the “this” keyword work?

Felix Kling
– Felix Kling

2017-03-06 17:22:19 +00:00
Commented Mar 6, 2017 at 17:22 — Felix Kling
– Felix Kling, Commented Mar 6, 2017 at 17:22

T.J. Crowder · Accepted Answer · 2017-03-06 17:38:53Z

13

Because NodeJS runs your code in a module, and this references the object it creates for your module's exports (which is also the exports property on the module variable it provides you). (As they don't really mention that in the module documentation, I suspect using it is probably not a great idea — use exports instead.)

But your code calling the IIFE calls it with this referring to the global object, because in loose (non-strict) mode, calling a normal function not through an object property calls it with this set to the global object. (In strict mode, this would be undefined there.)

edited Mar 6, 2017 at 17:38

answered Mar 6, 2017 at 17:19

T.J. Crowder

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2 Comments

Dan Lowe Over a year ago

Note, if you run without a module it does print contents of global. Example: node -e 'console.log(this)'.

T.J. Crowder Over a year ago

@DanLowe: Learn something new every day, I didn't realize immediate code was run at global scope, outside of a module. But you're right, it is (and thus this refers to the global object).

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