[SOLVED] Is there anyway to have a filesystem-like facility on ESP8266?

I am totally sure that I tried above ...require("FlashEEPROM")... code a few hours ago and it returned an object, but now it fails with following error message:

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Flash map 512KB:256/256, manuf 0xe0 chip 0x4014
>require("FlashEEPROM")
WARNING: Module "FlashEEPROM" not found
=undefined
>