Variable scope on this returns undefined in node.js

Question

Why is it that within Google Chrome, if I open the console and put in the following logic...

function foo() {
    console.log( this.bar );
}

var bar = "global";
foo();

...I get "global" as a result for calling foo();

But if I place the same logic into a file called app.js within Visual Studio Code, and from the terminal run node app.js, I get undefined ?

Additionally to what @SLaks said: browsers consoles are unique environments with a lot of tiny nuances: if you want to ensure something works as expected - put your js in a <script> tag and run. — zerkms
– zerkms, Commented Jan 10, 2018 at 22:05
ahhh - That may be a good thing if I am trying to avoid implicit globals overall in my understanding of JavaScript. Thank you node.js for preventive measures! — klewis
– klewis, Commented Jan 10, 2018 at 22:14
In a browser, the global window object is the default context for this. — Barmar
– Barmar, Commented Jan 10, 2018 at 23:10

亚里士朱德 · Accepted Answer · 2018-01-10 23:24:27Z

1

In browser

function foo() {
    console.log( this.bar ); //"this" point to "window" it equals to: console.log(window.bar)
}

var bar = "global";
foo();

In Node.js

function foo() {
    console.log( this.bar );
}

bar = "global"; //implicit declaration variable will be global object's property
foo();

answered Jan 10, 2018 at 23:24

亚里士朱德

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