CODEWITHSUNDEEP
arraystypescriptundefined
Erian
Erian

Reputation: 25

'Object is possibly undefined' for items in an array

I know there are a lot of questions about 'Object is possibly undefined' errors in typescript, but I have not found an answer to my particular question. I have an array with items and I want to access an element by index. I can put checks for each part of the element I want to access in an if statement around it, but it will still tell me that it is possibly undefined.

My code looks like this:

if(this.classLevels && this.classLevels[finalLevel] && this.classLevels[finalLevel].class){
    this.classLevels[finalLevel].class.currentLevel += 1;
}

class seems to be what can be undefined. It automatically wants to put a questionmark there, like this.classLevels[finalLevel].class?.currentLevel += 1;, but in that case I get the error that The left-hand side of an assignment expression may not be an optional property access.

I don't really want to disable the strict undefined check, but if I cannot get it to work with elements in an array, I may have to. Is there something I am missing here?

Upvotes: 0

Views: 6398

Answers (1)

spender
spender

Reputation: 120400

Assuming that you have noUncheckedIndexedAccess enabled, your best bet would be to make an intermediate variable:

const finalLevelClass = this.classLevels?.[finalLevel]?.class;

if (finalLevelClass) {
    finalLevelClass.currentLevel += 1;
}

Upvotes: 3

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