❗️Что будет на выходе:

const weakMap = new WeakMap();
const arr = [{}, {}, {}, []];

arr.forEach((obj, index) => weakMap.set(obj, index));

arr.splice(1, 1);

const result = arr.map(obj => weakMap.get(obj));

console.log(result);

Ответ:
[ {} ]
[ 0, 2, 3 ]

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