JavaScript TypeError – Property “X” is non-configurable and can’t be deleted
This JavaScript exception property is non-configurable and can’t be deleted if the user tries to delete a property, and the property is non-configurable.
Message:
TypeError: Calling delete on 'x' is not allowed in strict mode (Edge) TypeError: property "x" is non-configurable and can't be deleted. (Firefox) TypeError: Cannot delete property 'x' of #<Object> (Chrome)
Error Type:
TypeError
Cause of Error: There is an attempt to delete a property that is non-configurable.
Example 1: In this example, the delete is used to delete a non-configurable property, So the error has occurred.
HTML
<script> 'use strict'; var GFG_Obj = Object.freeze({prop1: 'val1', prop2: 123}); delete GFG_Obj.prop2; // Error here</script> |
Output(in console):
TypeError: Calling delete on 'prop2' is not allowed in strict mode
Example 2: In this example, the delete is used to delete PI which is a non-configurable property, So the error has occurred.
HTML
<script> 'use strict'; delete Math.PI; // Error here</script> |
Output(in console):
TypeError: Calling delete on 'PI' is not allowed in strict mode
