How to realize consultation in browser active message push pop-up window

how is this pop-up window realized? I didn"t even visit Websocket? on this site. What if the back end also wants to send information to the front-end interface such as "XX task is complete" in this way?

can this information tell the difference between a broadcast or a specific user?

Apr.06,2021

PWA
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Push API + Notifications API .

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e46b34-44bc3.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e46b34-44bc3.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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