How to create an array of objects with all objects from multiple arrays?

February 9, 2022

Given de following arrays:

const classes = [
  {
    students: [
       Student1,
       Student2,
    ]
  },
  {
    students: [
       Student3,
       Student4,
    ]
  }
]

What’s the best way performance-wise to generate an array of objects with a similar structure to this:

const allStudents = [
  Student1,
  Student2,
  Student3,
  Student4
]

>Solution :

Please note: Donot use reserved keyworks such ass class as a variable name.

Array.reduce implementation

const classes = [
  { students: [ 'Student1', 'Student2' ] },
  { students: [ 'Student3', 'Student4' ] }
];
const allStudents = classes.reduce((acc, cls) => {
  acc = cls.students ? acc.concat(cls.students) : acc;
  return acc;
}, []);
console.log(allStudents)

Array.flatMap implementation.

const classes = [
  { students: [ 'Student1', 'Student2' ] },
  { students: [ 'Student3', 'Student4' ] }
]
const allStudents = classes.flatMap((cls) => cls.students ? cls.students : []);
console.log(allStudents);