Save the contents of an array

Question

If we have, for example, this code:

var a=[2,8,7];
var b=a;
a.shift();
document.write(b);

The output will be "8,7".
Well, I applied a change to "a", why exactly did "b" also change?
And how to save the contents of the array before applying changes to the array itself?

Answer 1

var a = [2,8,7];
var b = a; // b refers to the address of a
var c = [...a]; // creates an new array c that does no longer refer to a
a.shift();
console.log("a", a)
console.log("b", b);
console.log("c", c);

/*
here some examples how to copy an array:
https://holycoders.com/javscript-copy-array/
*/