Should warn about memory leaks potentials

[GrosSacASac]

https://mythbusters.js.org/#/v8-tips/freeing-memory

using

var foo = { bar: 'hello world' }
foo.bar = undefined // Efficient way (good)

can lead to memory leaks because foo keeps the string key "bar" stored potentially forever. Can happen when objects are used as maps.

[Kikobeats]

not sure if I understand you, the point here is

foo.bar = undefined // Efficient way (good)

instead of

delete foo.bar // Inefficient way (bad)

you keep bar reference in the object, but this is less aggresive than delete the key for the garbage collector.