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[Vue.js] computed value in vue wont load to template when value exist

there is this issue i see first in vue. there is a computed property:

numOfStudentsPerSubject() {
let res = []

for (let subject of this.subjects) {
let key = subject.superSubject.trim()
res[key] = 0
for (let student of this.students) {
let studentSubject = student.subjects.find((x) => x.superSubjectName === key)
if (studentSubject) res[key]++
return res

what is logged to the screen is the following result:

[Letters Recognition: 8, Listening - First Letter: 8, Listening - Letters: 0, Reading Comprehension - Sentences: 8, Reading Comprehension - Story: 8,]

but when i try to pint data to the screen like :<p>{numOfStudentsPerSubject}</p> it shows an empty array [] no matter what i do. anyone has any idea what can cause such an issue?

Solution :

First off you should be using an object for res and not an array. Arrays are indexed numerically and not by keys whereas objects are a collection of key value pairs.

Secondly, you are returning that array yet the vue.js template is expecting a string so is just calling toString on the array which defaults to [] as you don’t have any valid indexes to enumerate.

Switch to using an object and stringify that object (or use another method to convert it to a string) when you use it in the template.

const obj = {
‘example1’: 4,
‘example2’: 7