Js basis, I would like to ask you why console.log reported these three numbers, what is the principle?

var a = {};
var b = {key: "b"};
var c = {key: "c"};
var d = [3,5,6];
a[b] = 123;
a[c] = 345;
a[d] = 333;
console.log(a[b]);  // 345
console.log(a[c]);  // 345
console.log(a[d]);  // 333
Feb.28,2021

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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-64f5-1b378b0-e5f0.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b378b0-e5f0.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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