I recently encountered a Typescript warning when sorting an array of objects based on one of their properties. Although the sorting is functioning properly, the warning "'Object is possibly 'undefined'' keeps appearing.
What is the best method to verify and manage undefined values for the 'name' property in order to address this warning?
myItems.sort((a, b) => (a.name > b.name ? 1 : -1));
Typescript is alerting you to a potential bug in your code. It seems that the type of your array is structured as follows:
({ name: string } | undefined)[]
This indicates that when you loop through the array, you must account for cases where the item may be undefined. Failure to do so could result in a runtime error when trying to access (undefined).name.
An effective solution is to filter out any undefined values from your array:
interface MyItem { name: string }
const myItems: (MyItem | undefined)[] = [
{ name: 'c' },
{ name: 'b' },
undefined,
{ name: 'a' },
]
myItems
.filter((item): item is MyItem => !!item)
.sort((a, b) => (a.name > b.name ? 1 : -1));
This approach utilizes a filter function acting as a typeguard. Once applied, the resulting array will be of type MyItem[], enabling successful sorting knowing all items contain a value.
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