Question

I have this code below:

this.color = "red";
var o = {color: "blue"};
function sayColor() {
  console.log(this.color);
}
sayColor();
sayColor.call(this);
sayColor.call(o);

@Jim Deville,

here are the new discoveries:

1. when I run that code snippet in browser: it outputs “red, red, blue”, continuously.
2. when I run it directly in node terminal: it also outputs “red, red, blue”, continuously.
3. but when I save that code in as a file functionTypeThisExample.js, and execute node functionTypeThisExample.js in terminal, it outputs “undefined, red, blue”.

so my question is what happens in last situation?

Answer 1

this in node is no different than this in JS. It is the object representing the current context.

this.color = "red";

Here, this is the global object

var o = {color: "blue"};
function sayColor() {
  console.log(this.color);
}

sayColor();

In this case, this is still the global object

sayColor.call(this);

This is the global object, but applied via call, not “by default”

sayColor.call(o);

This is o

When I run it in node (0.6.18 on OS X), though, I get “red, red, blue” like you do in the browser.