How to loop through an object of arrays in Javascript?

Question

For the below code,

const groupbysubject = {
 "Mathematics":
 [
 {totalStudents: "23", average: "78", class: "2"},
 {totalStudents: "25", average: "80", class: "3"}
 ],
 "English":
 [
 {totalStudents: "33", average: "98", class: "2"},
 {totalStudents: "35", average: "99", class: "3"}
 ],
 "Science":
 [
 {totalStudents: "43", average: "65", class: "2"},
 ]
 }
 
var isEnglishPresent = Object.fromEntries(
 Object.entries(groupbysubject).filter(
 ([key, val])=> key.includes("English")
 )
 );

I want the following output :

"33" "98" "2" "35" "99" "3"

I have filtered the above groupbysubject object into isEnglishPresent object. How do I proceed further to iterate over isEnglishPresent and get the above output. Please help

Thank you.

Answer 1

You want a flat list of the values from the items inside the English key:

const groupbysubject = {
 "Mathematics":
 [
 {totalStudents: "23", average: "78", class: "2"},
 {totalStudents: "25", average: "80", class: "3"}
 ],
 "English":
 [
 {totalStudents: "33", average: "98", class: "2"},
 {totalStudents: "35", average: "99", class: "3"}
 ],
 "Science":
 [
 {totalStudents: "43", average: "65", class: "2"},
 ]
};
var englishData = groupbysubject.English.flatMap(item => Object.values(item));
console.log(englishData);

• user13692230: Thank you but what if the in the output we only need totalStudents of English. How will we do that then?
• Tomalak: @ApoorvaOjha Why did your question not say from the start what you need?
• Tomalak: Also, read my code, understand what it does, experiment a little, and you will figure it out. You don't depend on me making it copy-and-paste ready for you.
• Andus: Although my answer is being accepted, I appreciate this less code flatMap approach
• Tomalak: @Andus It's a moot point anyway, as it only solves the problem the OP asked for, not the problem the OP wanted to solve.

Answer 2

Assume you have an English array with N objects like below.

const English = [
 {totalStudents: "33", average: "98", class: "2"},
 {totalStudents: "35", average: "99", class: "3"},
 ...
]

Here's how you extract all the values and put it into an array.

English.map(item => Object.values(item)).flat()

Here's the output

["33", "98", "2", "35", "99", "3"]

• Roko C. Buljan: Instead of .map() followed by .flat() there's the Array.prototype.flatMap()