A challenge of "Spread Operator" works well even if I don't put the Spread Operator

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1

A challenge of “Spread Operator” works well even if I don’t put the Spread Operator:
CHALLENGE: " ES6: Use the Spread Operator to Evaluate Arrays In-Place"
I have commented/deleted the right code and put another code without Spread Operator >> The challenge passed successfully!

Tip 2 didn’t implemented as well: ... spread operator should be used to duplicate arr1 .

The Code mentioned below


const arr1 = ['JAN', 'FEB', 'MAR', 'APR', 'MAY'];
let arr2;

// arr2 = [...arr1];  // Change this line
arr2 = arr1;
console.log(arr2);

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Challenge: Use the Spread Operator to Evaluate Arrays In-Place

Link to the challenge:

2

It looks like this only works because you have the correct answer commented out.

3

It works even if I deleted the commented code.

4

Can you show me code that passes with that line deleted? If I copy and paste your code and delete the line

// arr2 = [...arr1];  // Change this line

then it fails.

1 Like
5

Maybe It worked well because I run it twice,
first time with the commented code and the second when it was deleted…

6

This is because they both do the same thing, but you were required to use the spread operator for this particular exercise.

arr2 = arr1 (copies arr1 to arr2)
arr2 = […arr1] (spread operator)

7

The do not do the same thing.

arr2 = arr1 makes a shallow copy. If you make changes in arr2, then arr1 is changed.

arr2 = [...arr1] makes a deep copy. If you make changes in arr2, then arr1 is unchanged.

It’s a small piece of syntax that can cause huge headaches in debugging.

2 Likes
8

I have moved this to the #contributors sub-forum.

Whilst the mentioned solution is incorrect, it does not go against the aim of the lesson - teaching students to use the spread operator. Yes, you have not done as expected, but you had to write the code necessary to make a shallow copy (albeit in comment). So, clearly, you understood the use of the operator.

All in all, I do not see a need to change the tests.