Filter array of objects based on value of an inside array

Question

I want to select from array courses only the courses that have at least one field with id in fieldIds array. bellow is the format of thw arrays:

courses = [
    {id: 5, name:"some name1", fields:[{id: 28, name:"field name"}, {id: 29, name:"field name2"}]},
    {id: 18, name:"some name2", fields:[{id: 11, name:"field name"}, {id: 28, name:"field name2"}]},
    {id: 7, name:"some name3", fields:[{id: 29, name:"field name"}, {id: 9, name:"field name2"}]}
]

fieldIds = [29, 9]

So the result should be:

courses = [
    {id: 5, name:"some name1", fields:[{id: 28, name:"field name"}, {id: 29, name:"field name2"}]},
    {id: 7, name:"some name3", fields:[{id: 29, name:"field name"}, {id: 9, name:"field name2"}]}
]

This is what I tried and I always got the same array it changes nothing

fieldIds.map(fieldId => {
    courses = courses.filter(course => course.fields.map(f => f.id == fieldId);
});

EDIT after trying the response of this question as follow:

fieldIds.map(fieldId => {
    courses = courses.filter(course => course.fields.some(f => f.id == fielded))
}

if the fieldIds contain a couple of IDs for example the function returns courses belong to all fields. (and I want to extract the courses that have at least one of the selected fields)

Try to explain what your script does and you might get an idea why it doesn't work as expected. Why fieldIds.map(...) Why course.fields.map(...)? — Andreas
– Andreas, Commented Sep 10, 2020 at 13:50
Does this answer your question? Filtering array based on nested property — Heretic Monkey
– Heretic Monkey, Commented Sep 10, 2020 at 13:56

Carlo Corradini · Accepted Answer · 2020-09-10 14:20:50Z

2

Here is the working solution:

const courses = [
    {id: 5, name:"some name1", fields:[{id: 28, name:"field name"}, {id: 29, name:"field name2"}]},
    {id: 18, name:"some name2", fields:[{id: 11, name:"field name"}, {id: 28, name:"field name2"}]},
    {id: 7, name:"some name3", fields:[{id: 29, name:"field name"}, {id: 9, name:"field name2"}]}
];

const fieldIds = [29, 9];

const filtered_courses = courses.filter(course => course.fields.some(field => fieldIds.includes(field.id)));

console.log(filtered_courses);

Filter the courses array with the condition (some) verifying that at least one element in the fields array has an equal value from fieldIds array.

PS: If fields array(s) and fieldIds array are sorted in ASC or DESC order the "algorithm" is much faster since the some method return earlier.

edited Sep 10, 2020 at 14:20

answered Sep 10, 2020 at 14:15

Carlo Corradini

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