getting error "Expected false to be true"

Question

i have function called sunset that copies the existing array sunsetColors by reference and then changes the first element to "blue". sunset should return the copy of the array.


function sunset(){
  let clone =sunsetColors;
clone.splice(0,0,"blue");
  return clone;
}
sunset()

well it is not a copy.... `console.log(sunsetColors, clone)` — epascarello, May 31 '19 at 16:44
https://stackoverflow.com/questions/7486085/copy-array-by-value — epascarello, May 31 '19 at 16:46
@Divya just add it with destructuring as such `[ "blue", ...sunsetColors ]` — darklightcode, May 31 '19 at 16:46
@darklightcode does that replace the first element with "blue"? — GrafiCode, May 31 '19 at 16:48
It will create a new array where "blue" is at position 0 and the rest of the elements will be added by the `...`(spread operator) — darklightcode, May 31 '19 at 16:49
but i am getting "sunset should create a copy by reference and change the first element to blue" failure message — Divya, May 31 '19 at 16:49
@darklightcode OP asked "and then changes the first element to 'blue'" — GrafiCode, May 31 '19 at 16:50
thats what this code do right ? [ "blue", ...sunsetColors ] changing the first element to "blue" — Divya, May 31 '19 at 16:53
@Divya it actually prepends "blue" to the array, as first element. When you say `change`, you mean `replace the first element` or `place at the beginning`? — GrafiCode, May 31 '19 at 16:54
My apologies, i may have misread , try this, `clone.splice(0,1,"blue");` , the second parameter of `.splice` will replace the item from position 0 in `clone`. If that doesn't help. Please provide us a sample of `sunsetColors` and the expected outcome. — darklightcode, May 31 '19 at 16:56
i tried that already , but i am still getting "sunset should create a copy by reference and change the first element to blue" " sunset should not change the rest of the array" "Expected false to be true." — Divya, May 31 '19 at 16:59
If you have an array like `let arr = ['red', 'yellow']`, then you can copy it like `let clone = arr.slice()`. Then you can change the first element of the copy like `clone[0] = 'blue'`. — benvc, May 31 '19 at 17:10
i just changed to this and it worked. ``` function sunset() { sunsetColors[0] = "blue"; return (clone = sunsetColors.slice()); } sunset(); ``` thank you all... — Divya, May 31 '19 at 17:10

score 1 · Answer 1 · answered May 31 '19 at 17:34

1

try the following code for cloning

let clone = JSON.parse(JSON.stringify(sunsetColors));

Here is a very good article for array cloning in Javascript.

https://www.freecodecamp.org/news/how-to-clone-an-array-in-javascript-1d3183468f6a/

answered May 31 '19 at 17:34

Jayant Varshney

1,765
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Dan Cron · Answer 2 · 2019-05-31T17:39:51.597

0

This does not copy the array.

let clone =sunsetColors;

At the end of that statement, clone and sunsetColors are both pointing to the same array.

To copy the array, try something such as

let clone = [...sunsetColors];

Or you could copy the array this way

let clone = sunsetColors.slice();

edited May 31 '19 at 17:39

answered May 31 '19 at 17:30

Dan Cron

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getting error "Expected false to be true"

2 Answers2