I am experiencing unexpected behaviour of push function. The problem is with the latest line of code cited below.
export enum non_searchFieldsNames {
language = 'language',
categories = 'categories',
subtitle = 'subtitle',
publishedDate = 'publishedDate',
id = 'id',
}
enum columnsEnum {
title,
authors,
language,
categories,
subtitle,
publishedDate,
}
function toArray(obj: header | contentCategories | sourceFields) {
return Object.entries(obj)
.sort((a, b) => {
return +a - +b;
})
.map(item => item[1]);
}
let sourceFieldsObject: sourceFields = {
[columnsEnum.title]: searchFieldsNames.title,
[columnsEnum.authors]: searchFieldsNames.authors,
[columnsEnum.language]: non_searchFieldsNames.language,
[columnsEnum.categories]: non_searchFieldsNames.categories,
[columnsEnum.subtitle]: non_searchFieldsNames.subtitle,
[columnsEnum.publishedDate]: non_searchFieldsNames.publishedDate,
};
const sourceFieldsArray = toArray(sourceFieldsObject).push(non_searchFieldsNames.id);
The problem is with the latest line of code. The value I do receive here is 7. When I simplify it like this
const sourceFieldsArray = toArray(sourceFieldsObject)
I receive an array(however, without the value I try to add, of course).
When I split the logic
const sourceFieldsArray = (toArray(sourceFieldsObject));
sourceFieldsArray.push(non_searchFieldsNames.id);
I get what I wanted. Anyway, I would like to have it as one-liner. So, what is my error? I have tried also
const sourceFieldsArray (toArray(sourceFieldsObject)).push(non_searchFieldsNames.id)
But it does not help.
push modifies the main array directly, and it does not return a new array as you expected, but the count of items in that array.
You can check the below demo for push's returned value
const array = [1,1,1] //3 items
const count = array.push(1) //1 more item
console.log(count) //total is 4 itemsIf you want to have a one-liner, you can try the cloning approach with the spreading operator
const sourceFieldsArray = [...toArray(sourceFieldsObject), non_searchFieldsNames.id]
Side note that this approach means you're creating a new array completely, so you need to be aware of some performance situations with a huge array.