Where this matters
Slice is useful for displaying a portion of a list while preserving the original list. Its second argument is an exclusive index, not a count.
JavaScript · read-only example
const values = [1, 2, 3];
console.log(JSON.stringify(values.slice(0, 2)));
console.log(JSON.stringify(values));Read the full explanation
Slice includes index zero and excludes index two. It returns a shallow copy without removing elements from the input.
Trace the code
- Index 0 contains 1 and index 1 contains 2.
- Index 2 is the stopping boundary and is not included.
- The new array contains the selected entries; the source array keeps all three. Nested objects would still be shared.
Why the other predictions differ
[1,2,3] [1,2,3]— The ending index is excluded.[1,2] [3]— Slice does not mutate; splice is a different method.
[1,2] [1,2,3]
Reading this explanation does not record mastery. A correct submitted attempt can do so, including after review.
Change one thing
Move the starting index to 1 and leave the end at 2.
Predict the result, then run this self-contained snippet in your browser’s developer console. It uses only sample values and makes no network requests.
console.log(JSON.stringify([1, 2, 3].slice(1, 2)));Check the variation’s output
[2]
Explain which binding, value, or operation changed before moving to the next challenge.