Unexpected Javascript array behavior

Question

I signed the variable bubbleL1 to 1, but why the first variable in the bubbles list, which is bubbleL1 still shows undefined? I know this maybe a stupid question, but I really don't know why.

    let bubbleL1, bubbleL2, bubbleL3, bubbleR1, bubbleR2, bubbleR3;
    let bubbles = [bubbleL1, bubbleL2, bubbleL3, bubbleR1, bubbleR2, bubbleR3];

    bubbleL1 = 1;
    console.log(bubbleL1) // 1
    console.log(bubbles) // [undefined, undefined, undefined, undefined, undefined, undefined]

What I want is a list with a specific name for each item in it (for the declared reason, I really don't just use bubbles[0], bubbles[1]...)

Let's say we have a list named bubbles, and we also have six variables called bubbleL1, bubbleL2, bubbleL3, bubbleR1, bubbleR2, bubbleR3. I want to put all these six variables into the bubbles list, so later I can assign values to each variables that in the list, like this:

bubbles.forEach((bubble) => {
  bubble = "something";
})

https://stackoverflow.com/questions/518000/is-javascript-a-pass-by-reference-or-pass-by-value-language — epascarello, Jun 28 '19 at 14:59

junvar · Accepted Answer · 2019-06-28T15:02:39.423

3

bubbleL1 is a primitive and therefore copied by value.

let x = 3;

let sum = x;
sum = 3 + 5;

console.log(x); // 3

Objects and arrays, on the other hand, will exhibit your expected copy-by-ref behavior:

let x = {a: 3};

let sum = x;
sum.a = 3 + 5;

console.log(x.a); // 8

edited Jun 28 '19 at 15:02

answered Jun 28 '19 at 14:59

junvar

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Unexpected Javascript array behavior

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