Hi new learner here, why doesnt javascript code from sololearn work elsewhere?

Question

im trying out the Javascript code in repl.it and other sites and they not working.

THis makes me worry that im learning JS wrong. Why is this happening?

what am i missing?

all saying thing like document not defined

for Example the for loops code on other sites give error:
"for (i=1; i<=5; i++) {
document.write(i + "<br />");
}

ReferenceError: document is not defined
at Object.<anonymous> (/home/runner/UtterLoyalAutotote/index.js:2:5)
at Module._compile (node:internal/modules/cjs/loader:1105:14)

And another example else if statement :

var course = 1;
if (course == 1) {
document.write("<h1>HTML Tutorial</h1>");
} else if (course == 2) {
document.write("<h1>CSS Tutorial</h1>");
} else {
document.write("<h1>JavaScript Tutorial</h1>");
}

ReferenceError: document is not defined
at Object.<anonymous> (/home/runner/UtterLoyalAutotote/index.js:3:5)
at Module._compile (node:internal/modules/cjs/loader:1105:14)

Answer 1

JavaScript has two distinct uses:
- running in the web browser (client side)
- running in Node.js (server side)

The "document" object refers to the web browser's context of the current webpage that is opened. If you try to modify the DOM (document object model) from Node, it won't work because there is no webpage in this context.

In Node.js use console.log() to output data to the console.

Answer 2

Thank you very much tibor