JS Make deep copy of array

Question

Is there any way I can make a deep copy of a variable? (NOT object). Example:

var a = ["String", "string"];
var b = a;

b.splice(1, 1);

b = a;

In my example, a isnt supposed to change, I want to use it later for restoring b. (As showed in code above).

I understand that = just makes a new reference, hence the question: is there any other way I can make a deep copy instead of a reference?

Want to note that I can't be using any library, I've found answers suggesting jQuery and such, but I cannot use this.

It's only objects in javascript (arrays are objects too) that gets references to each other. All other variable types are new variables. — Rickard Elimää, Mar 12 '18 at 12:38
@RickardElimää Sorry, the example was really poor, fixed now — Chaost, Mar 12 '18 at 12:40

Aurel Bílý · Answer 1 · 2018-03-12T12:41:31.050

2

Have you tested your code? Numbers and other primitives are copied, not referenced.

var a = 1;
var b = a;
console.log(`a is ${a}`);
console.log(`b is ${b}`);
b++;
console.log(`a is ${a} (no change)`);
console.log(`b is ${b}`);

After your edit with a different example:

var a = ["foo", "bar"];
var b = a.slice(); // array copy
console.log(`a is ${a}`);
console.log(`b is ${b}`);
b.splice(1, 1);
console.log(`a is ${a} (not changed)`);
console.log(`b is ${b}`);
b = a;

edited Mar 12 '18 at 12:41

answered Mar 12 '18 at 12:37

Aurel Bílý

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That's my bad, really poor example, in my case I'm handling string arrays, which I have tested – Chaost Mar 12 '18 at 12:38
@Chaost An array is not a primitive but an object. – str Mar 12 '18 at 12:39
@Chaost Well a string array (array of strings?) is just an object, so refer to deep-copying arrays. – Aurel Bílý Mar 12 '18 at 12:39
@AurelBílý oh didn't notice the `var b = a;` – Medet Tleukabiluly Mar 12 '18 at 12:41
Try by this line: var b = Object.assign([], a); – Hanif Mar 12 '18 at 12:48

JS Make deep copy of array

1 Answers1