?
Rustのquestion mark operator
https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator
error propagation演算子
"? operator"のほうが一般的
ECMAScript spec内でReturnIfAbruptの実行を表す記号(ReturnIfAbrupt Shorthands)
https://tc39.es/ecma262/#sec-returnifabrupt-shorthands
TypeScriptでのOptional Parameters、Optional Properties
https://www.typescriptlang.org/docs/handbook/functions.html#optional-and-default-parameters
https://www.typescriptlang.org/docs/handbook/interfaces.html#optional-properties
関連
??
?:
TypeScriptでのOptional Properties
ex, foo?: string
:?
Rustでのdebug formatのmarker
https://doc.rust-lang.org/rust-by-example/hello/print/print_debug.html
?.
JavaScriptでのOptional Chaining演算子