JSFiddle - React, Tailwind, and code Playground

JavaScript

function filter(array, f) { var r = []; for (var i in array) { if (f(array[i])) { r.push(array[i]); } } return r; }

function par(x) {return x % 2 == 0} 
var res = filter([1,2,3,4,5], par);    
console.log(res)    //[2,4]


var amigos = [{name: 'pepe',edad: 52},{name: 'ruben',edad: 12},{name: 'oscar',edad: 32}];

    var amigosMayores = filter(amigos, function(p){
        return p.edad > 18
    })

    console.log(amigosMayores) //pepe y oscar