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reference type (Array) question

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Aug 22.2007

Hello, I am a javascript learner, I have a question to confuse.

[CODE]
var a = [1,2,3];
var b = a;
a[0] = 99;
alert(b);
[/CODE]

The alert output is : 99,2,3

If I really want to copy value of a into b variable, how can I do ?

( I mean, if I want to use copy way, then the alert output can show 1,2,3
how to write the javascript?? or javascript can’t do that ??)

Thanks!

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JavaScript

4 Comments(s) ↴

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@toicontienAug 22.2007 — The code you posted is working correctly. Are you wanting to copy the whole array from one variable to another, or do you want to copy just one item from array "a" to array "b"?

To copy one item from one array to the next:
var a = [1,2,3];
var b = [35];
b[1] = a[1];

alert(b); // Shows 35,2
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@Mr_MooAug 22.2007 — <i>
</i>function copyArray(arr) {
var res = [];
for(var i = 0; i &lt; arr.length; ++i) {
res[i] = arr[i];
}
return res;
}
var a = [1,2,3];
var b = copyArray(a);
a[0] = 99;
alert(b);

The function copyArray makes a shallow copy of the array (meaning that if the array contains objects, and you change part of the object in the original array you will also change it in the copied array).
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@KitshingauthorAug 23.2007 — Thanks for toicontien and Mr Moo

~ The answer of Mr Moo is totally meet my request.

Thank a lot~
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@KitshingauthorApr 02.2008 — oh...

This post was almost a year ago,

Anyway, I found another way to copy array at recently.

[CODE]
var a = [1,2,3];
var b = a.slice();
a[0] = 99;
alert(b);
[/CODE]

Using slice() method, that will actually copy one to variable b. ?
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