ES6
'use strict'; var family = [ {'name':'Namihei', 'age': 54}, {'name':'Masuo', 'age': 28}, {'name':'Katsuo', 'age': 11}, {'name':'Tarao', 'age': 3} ]; var family1 = family.filter(function(person) { return person.age < 30; }); var family2 = family.filter((person) => { return person.age < 20; }); var family3 = family.filter(person => person.age < 10); console.log(family1); //=> [ { name: 'Masuo', age: 28 }, { name: 'Katsuo', age: 11 }, { name: 'Tarao', age: 3 } ] console.log(family2); //=> [ { name: 'Katsuo', age: 11 }, { name: 'Tarao', age: 3 } ] console.log(family3); //=> [ { name: 'Tarao', age: 3 } ]