At 'Stand in line' lesson in Basic JavaScript, testArr is a const

JavaScript
1

Tell us what’s happening:

At https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/basic-javascript/stand-in-line, the testArr variable is declared as a constant ― even if I press ‘Reset All Code’ followed ‘Reset This Lesson’, it is so.

This wouldn’t be really a problem if it weren’t for the first two comments that also come by default: “Only change code below/above this line”.

Should this be like it is?


function nextInLine(arr, item) {
// Only change code below this line
arr = arr.concat(item);
item = arr.shift()
// testArr = arr;
return item;
// Only change code above this line
}

// Setup
const testArr = [1, 2, 3, 4, 5];

// Display code
console.log("Before: " + JSON.stringify(testArr));
console.log(nextInLine(testArr, 6));
console.log("After: " + JSON.stringify(testArr));

Your browser information:

User Agent is: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:96.0) Gecko/20100101 Firefox/96.0

Challenge: Stand in Line

Link to the challenge:

2

Why do you think that the array being const is a problem?

3

The Lesson can be completed by declaring testArr with var or let at the Setup btw. It’s just the comments that made me confused.

4

You don’t need to make any changes to testArr. You should not touch any global variables. If you can pass this challenge by modifying a global variable, that is a bug in the test suite.

5

I wasn’t really sure about the post, sorry. What led me to make it was that running it as it is (the first one) always results in After nextInLine(testArr, 10), testArr[4] should be 10, where just changing testArr to let or var and uncommenting line 5 completed the lesson.

6

If that’s the case, that is a bug. Zero changes below that line are needed.

7

Even then, at // Display code, since testArr is a const and can’t be altered, what is the use of of console.log("After: " + JSON.stringify(testArr));?

8

const doesn’t mean you can’t change the contents of the array, only which array your variable points at.

1 Like
9

Oh, I think I understand now then. My solution didn’t work because concat fuses two arrays, and creates a new one? And that doesn’t work since const?

The solution provided at freeCodeCamp Challenge Guide: Stand in Line worked just fine without alterations to the Setup, and the // Display code shows the changes properly.

My mistake, sorry and thanks for the help.

10

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