Why does this code not work, despite not getting any errors

Question

1.00/5 (1 vote)

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I was trying to solve a puzzle, using javascript. currently, this code doesn't run, at all. I tried to tweak the numbers in the for loops, but the page doesn't want to load. I have tried to remove the script part of the HTML, and it loaded, so I know at least that the code below is the problem.

JavaScript

var lockers = [];

function studentAI(id, locker) {
    if (locker % id && locker >= id) {
        if (lockers[id] = false) {
            lockers[id] = true;

        } else {
            lockers[id] = false;
        }

    }

}

for (var student = 1; student <= 10; student++) {
    
    for (var locker = 1; locker <= 10; locker++) {
        if (student = 1) {
            lockers[locker] = true;
        } else {
            studentAI(student, locker);
        }
    }

}
for (let index = 0; index < lockers.length; index++) {
    console.log(lockers[index]);
}

Thanks!

What I have tried:

I tried to tweak the numbers in the for loops, but the page doesn't want to load. I have tried to remove the script part of the HTML, and it loaded, so I know at least that the code below is the problem.

Posted 11-Mar-22 11:55am

Hackcraft_

Updated 14-Mar-22 0:23am

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Luc Pattyn · Accepted Answer · 2022-03-11T13:50:00

Solution 1

ADDED: What follows is wrong, and not the solution!

if (locker % id && locker >= id) {

I can't even guess what is intended here, but it isn't acceptable JavaScript code.

&& is a diadic operator, it expects two boolean operands, things that are either true or false; locker % id is a number, not a boolean.

Posted 11-Mar-22 13:50pm

Luc Pattyn

Updated 14-Mar-22 0:38am

v3

Comments

Richard Deeming 14-Mar-22 6:18am

In most languages, that would be correct. But Javascript is "special" - the && operator will return true if both operands are "truthy" values.

Truthy - MDN Web Docs Glossary: Definitions of Web-related terms | MDN[^]

So locker % id && locker >= id is equivalent to (locker % id != 0) && locker >= id.

Luc Pattyn 14-Mar-22 6:40am

You're right of course; I forgot about the JavaScript idiosyncrasies.

Richard Deeming · Accepted Answer · 2022-03-14T00:23:00

Your script is hanging because you have introduced an infinite loop:

Quote:
JavaScript
if (student = 1) {

This statement sets the student variable to 1, and then tests whether the assigned value is truthy[^].

Your outer loop will never terminate, because on every iteration you are resetting the loop variable.

Javascript uses == (or ===) to test for equality:

JavaScript

if (student === 1) {