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I recently learned about optional chaining in Javascript and have been making use of it in a React/NodeJS project. Works great.
I noticed I have been using it with arrays map, even without thinking about it much -- it seemed a natural use (here items is an array, or possibly undefined)
{items?.map(postListItem => ....
That is, it will map if items exists, but not if items is undefined, but would avoid any run-time errors if I were to call map on undefined
Nonetheless I don't know if this is an acceptable use or whether I'm mis-using optional chaining. I searched for an answer but as of yet haven't been able to find one, which makes me suspect I'm mis-using it. Any info much appreciated!
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The optional chaining operator ( ?. ) enables you to read the value of a property located deep within a chain of connected objects without having to check that each reference in the chain is valid. The ?. operator is like the .
Introduction to the JavaScript optional chaining operator allows you to access the value of a property located deep within a chain of objects without explicitly checking if each reference in the chain is null or undefined .
Optional chaining is a process for querying and calling properties, methods, and subscripts on an optional that might currently be nil . If the optional contains a value, the property, method, or subscript call succeeds; if the optional is nil , the property, method, or subscript call returns nil .
Optional chaining was introduced in ES2020. According to TC39 it is currently at stage 4 of the proposal process and is prepared for inclusion in the final ECMAScript standard.
See answer here regarding the typescript usage. You need a period for array null safe Optional Chaining.
this.mostRecentMfaAttempt = this.verificationsAttempts?.content?.[0]
How to use optional chaining with array in Typescript?
Using optional chaining operator for object property access
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