I'm working with array in JavaScript, and my problem is working with variable reference. I have 2 examples below, and it seems to have the same result but it doesn't.
//Example 1
var arr = [1,2,3];
var refArr = arr;
arr[0] = 1;
arr[1] = 3;
arr[2] = 4;
console.log(arr); //[1,3,4];
console.log(refArr); //[1,3,4]
//Example 2
arr = [1,2,3];
refArr = arr;
arr = [1,3,4];
console.log(arr); //[1,3,4];
console.log(refArr); //[1,2,3]
I don't know what's the difference between 2 examples?
Up to refArr = [1,3,4], refArr and arr were referring to the same object. You change that object (by assigning to the properties 0, 1 and 2), you change the contents of both arr and refArr.
However, [1,3,4] is a different object that you just constructed there, and from that line onwards refArr refers to that object, and not the object referred to by arr.
An important thing to note is that there are no variable references in JavaScript, only object references. refArr does not refer to arr; both variables refer to the object represented as [1,2,3]. (Well, up to that line, anyway.)
This:
arr[0] = 1;
arr[1] = 3;
arr[2] = 4;
is not equivalent to this:
arr = [1,3,4];
In the first case, you're overwriting individual elements in the same parent array object.
In the second case, the entire array object is being replaced.
The fact the elements have the same value is irrelevant.
In the example 1: arr=refArr=[1,2,3](=originObject which stays in internal memory)， then you change the originObject, so arr and refArr both changed.
In the example 2: what's the different is that you assign arr to another originObject.
Mr.Thi Tran
when u declare and initialize an array like var arr = [1,2,3]; the variable 'arr' is in global scope ,
hence when u made any changes in to that reference will reflect others.
please correct me if i'm wrong.
