const employees = [{
name: 'John Olsen',
age: 54,
jobTitle: 'developer',
salary: 70000,
}, {
name: 'Karen Norris',
age: 34,
jobTitle: 'engineer',
salary: 75000,
}, {
name: 'Daryl Cline',
age: 25,
jobTitle: 'secretary',
salary: 54000,
}, {
name: 'Abbey Garcia',
age: 40,
jobTitle: 'developer',
salary: 100000,
}, {
name: 'Finn Smith',
age: 29,
jobTitle: 'engineer',
salary: 40000,
}, {
name: 'Eve Wordsworth',
age: 20,
jobTitle: 'developer',
salary: 65000,
}, {
name: 'Ronald Jacobs',
age: 60,
jobTitle: 'developer',
salary: 90000,
}];
const developers = employees.filter((employee) => 
employee.jobTitle === 'developer');
const developerSalaries = developers.map((developer) => 
developer.salary);
console.log('developerSalaries: ' +developerSalaries);
const totalDeveloperSalaries = 
developerSalaries.reduce((acc, x) => acc + x, 0);
console.log('totalDeveloperSalaries: '+totalDeveloperSalaries);
const averageDeveloperSalary = 
totalDeveloperSalaries / developerSalaries.length;
console.log("averageDeveloperSalary: "+averageDeveloperSalary);
const nonDevelopers = employees.filter((employee) => 
employee.jobTitle !== 'developer');
const nonDeveloperSalaries = nonDevelopers.map((nonDev) => 
nonDev.salary);
const totalNonDeveloperSalaries = 
nonDeveloperSalaries.reduce((acc, x) => acc + x, 0);
console.log('totalNonDeveloperSalaries: '+totalNonDeveloperSalaries );
const averageNonDeveloperSalary = 
totalNonDeveloperSalaries / nonDeveloperSalaries.length;
console.log("averageNonDeveloperSalary: "+averageNonDeveloperSalary);

Output:

developerSalaries: 70000,100000,65000,90000
examples.js:42
totalDeveloperSalaries: 325000
examples.js:46
averageDeveloperSalary: 81250
examples.js:50
totalNonDeveloperSalaries: 169000
examples.js:58
averageNonDeveloperSalary: 56333.333333333336