I have an array of objects:
const students = [
{ name: 'Tom', class: "Blue" },
{ name: 'Pom', class: "Blue" },
{ name: 'Max', class: "Red" },
{ name: 'Alex', class: "Red" },
{ name: 'John', class: "Yellow" }
];
And I would like to group the return values by the class property, so I can achieve something similar to this in HTML:
Class Blue: Tom, Pom
Class Red: Max, Alex
Class Yellow: John
note: the class property should be displayed once as HTML mark-up which is the reason I don't think 
CodePudding user response：
You could create a new object with the name of the classes as keys and an array with the names of the students as values.
const students = [
{ name: 'Tom', class: "Blue" },
{ name: 'Pom', class: "Blue" },
{ name: 'Max', class: "Red" },
{ name: 'Alex', class: "Red" },
{ name: 'John', class: "Yellow" }
];
let klasses = {};
for (let i = 0; i < students.length; i ) {
let student = students[i];
let klass = student.class;
if (!klasses[klass]) {
klasses[klass] = [student.name];
} else {
klasses[klass].push(student.name);
}
}
console.log(klasses);CodePudding user response：
let classes = {};
for(let student of students) {
classes[student.class] = [...classes[student.class] || [], student.name];
}
console.log(classes);