Cannot add property 0, object is not extensible

js

foo = []
Object.freeze(foo)
foo.push(1)
// Uncaught TypeError: Cannot add property 0, object is not extensible

Happens when trying to push against a frozen Array

Specific Occurrence Situations So why was it frozen?

The selected element is being put into ReactN and then frozen when it is taken out. Kindly designed to prevent inadvertent destructive updates and a nasty bug.

When grouping the selected ones, this is what was written, which is wrong ts

  const group = new GroupItem();
  group.items = g.selected_items;

This will cause the new group to have a reference to the frozen object itself, and then when you try to add to that group, you will get the above error.

ts

  group.items = [...g.selected_items];

This is what I should have done.

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