easy_questions.js

// simple assert
function assertEqual(a, b) {
    return a === b;
}

// input data
var spend = [
    {
        id: 1,
        price: -120,
        category: 'leisure',
        name: 'food'
    },
    {
        id: 2,
        price: -45.1,
        category: 'leisure',
        name: 'bevarage'
    },
    {
        id: 3,
        price: '250',
        category: 'income',
        name: 'return'
    },
    {
        id: 4,
        category: 'income',
        name: 'placeholder'
    }
];

// pick returns new list of values in field
function pick(list, field) {
}

// sum returns sum of all values by field
function sum(list) {
}

// find filters the input list of objects, based on key and value
function find(list, field, value) {
}

console.log(assertEqual(sum(pick(spend, 'price')), 84.9));
console.log(assertEqual(sum(pick(find(spend, 'category', 'leisure'), 'price')), -165.1));