What is scenario to set getOnInit option in atomWithStorage?

[xc1427]

I found this option somewhat confusing. Please correct me if I’m mistaken.

The documentation states:
getOnInit (optional, default: false): A boolean value indicating whether to retrieve the item from storage during initialization. Note that in an SPA, if getOnInit is either not set or set to false, the initial value will always be used instead of the stored value during initialization. To prefer the stored value, set getOnInit to true.

Consider the scenario where the local storage key is my_locale. Based on testing with v2.11.0, the behavior is as follows:

• When false: If my_locale is not defined, the atom is assigned the initialValue. If my_locale exists, even its value is null, the atom is first assigned initialValue then quickly updated to the local storage value after baseAtom.onMount is called, provided no exceptions occur during JSON parsing. (This behavior is confusing because, in most cases, the value ultimately comes from local storage.)
• When true: The value is explicitly retrieved from local storage unless an exception occurs during JSON parsing. (This behavior feels more predictable.)

In summary, this option primarily acts as a safeguard for cases where key in local storage is not defined. However, this behavior can be easily handled in user space with no ambiguity without relying on this option.

[dai-shi]

In short, Next.js users should use false, RN users would use true. We default to false because many people reported as bugs previously. false is required if you use SSR. If true works for your case, feel free to use it.