Javascript temporary variable value cleared once I cleared the original value..why?

Question

I copied an array to a temporary variable tempPropertyValuesArray

And then when I cleared the original array $scope.advancedSearch.businessCard.propertyValues

It also cleared the tempPropertyValuesArray

I am surprised. Is this the expected behavior ?

Javascript:

var tempPropertyValuesArray = $scope.advancedSearch.businessCard.propertyValues;
$log.debug("tempPropertyValuesArray 1 : " +tempPropertyValuesArray);
$scope.advancedSearch.businessCard.propertyValues.length = 0;
$log.debug("tempPropertyValuesArray 2 : " +tempPropertyValuesArray);

Logs:

tempPropertyValuesArray 1 : [object Object],[object Object] 
tempPropertyValuesArray 2 :

you are currently **referencing** it, not copying, it's different ;) — briosheje, Jul 29 '16 at 10:49

Jamiec · Accepted Answer · 2016-07-29T10:51:30.547

4

In a Javascript I copied an array to a temporary variable tempPropertyValuesArray

You didn't copy it, you made a reference to it. Changing the reference, changes the original object.

If you really want a copy, do this:

var tempPropertyValuesArray 
      = $scope.advancedSearch.businessCard.propertyValues.slice();

edited Jul 29 '16 at 10:51

answered Jul 29 '16 at 10:49

Jamiec

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Many thanks how can I copy please – Jay Jul 29 '16 at 10:50
@Jay - updated answer – Jamiec Jul 29 '16 at 10:50
1

`Array.prototype.slice` would be a whole lot simpler… – deceze Jul 29 '16 at 10:50
@deceze - pfft, of course it would. I must have had an id10t error. – Jamiec Jul 29 '16 at 10:51
But why take the simple route, right? – deceze Jul 29 '16 at 10:51
@Jamiec Thanks .slice() works. – Jay Jul 29 '16 at 10:56

Javascript temporary variable value cleared once I cleared the original value..why?

1 Answers1