JavaScript Interview Prep Practice Problems Part 2

function getTotal() {
    //convert object to an array
    var args = Array.prototype.slice.call(arguments);

    if (args.length === 2) {
        return args[0] + args[1];
    }
    else if (args.length === 1) {
        return function(num2) {
            return args[0] + num2;
        };
    }
}

console.log(getTotal(10, 20));
console.log(getTotal(5, 40));
console.log(getTotal(3)(30));
console.log(getTotal(8)(12));

30
45
33
20

Process finished with exit code 0

const myJsonObj = {
  "myString": "hello world",
  "myNumber": 12345.6789,
  "myNull": null,
  "myBoolean": true,
  "myArray": [20, 30, "orange"],
  "myObject": {
    "name": "Sam",
    "age": 30
  }
};

function logNumbers() {
    console.log(1);
    //added in event loop
    setTimeout(function(){console.log(2)}, 1000);
    //added in event loop
    setTimeout(function(){console.log(3)}, 0);
    console.log(4);
}

logNumbers();

1
4
3
2

Process finished with exit code 0

// object literal syntax
const myBoat = {
    length: 24,
    maxSpeed: 45,
    passengers: 14,
    getLength: function () {
        return this.length;
    }
};

// new keyword & Object constructor
const student = new Object();
// const student = {};

student.grade = 12;
student.gradePointAverage = 3.7;
student.classes = ["English", "Algebra", "Chemistry"];
student.getClasses = function () {
    return this.classes;
};

// constructor function 
function Car(color, brand, year) {
    this.color = color;
    this.brand = brand;
    this.year = year;
}

Car.prototype.getColor = function () {
    return this.color;
};

const carlysCar = new Car('blue', 'ferarri', 2015);
const jimsCar = new Car('red', 'tesla', 2014);

console.log(carlysCar.getColor());
console.log(jimsCar.getColor());

console.log(typeof null);       // object
console.log(typeof undefined);  // undefined
console.log(typeof {});         // object
console.log(typeof []);         // object
console.log(Array.isArray([])); // true
console.log([] instanceof Array);   // true

this.distance = 10000;
const roadTrip1 = {
    distance: 3000,
    getDistance: function (unit, caption) {
        return this.distance + unit + caption;
    }
};
const roadTrip2 = {
    distance: 5000
};
const getTripDistance = roadTrip1.getDistance.bind(roadTrip2, 'km',' in total');

console.log(getTripDistance())

// Output:
// 5000km in total
// Process finished with exit code 0

const user1 = {
    name: 'Jordan',
    age: 28,
};
const user2 = {
    name: 'Jordan',
    age: 28,
};

console.log(user1 == user2);
console.log([] == []); //array is object
console.log(JSON.stringify(user1) === JSON.stringify(user2));
// Output:
//  false
//  false
//  true
//  Process finished with exit code 0

var arr1 = [];
var arr2 = new Array(50); //initial an empty array with 50 length
var arr3 = new Array(1, 2, "three", 4, "five");
var arr4 = new Array([1, 2, 3, 4, 5]);
var arr5 = new Array('Hello world');

console.log('arr1: ', arr1);
console.log('arr2: ', arr2);
console.log('arr3: ', arr3);
console.log('arr4: ', arr4);
console.log('arr5: ', arr5);

arr1:  []
arr2:  [ <50 empty items> ]
arr3:  [ 1, 2, 'three', 4, 'five' ]
arr4:  [ [ 1, 2, 3, 4, 5 ] ]
arr5:  [ 'Hello world' ]

Process finished with exit code 0

const myArray = [5];
const anotherArray = myArray;

console.log([10, 20, 30, 40, 50].indexOf(30));  // 2
console.log([{ name: 'Pam' }, { name: 'Kent' }].indexOf({ name: 'Kent' })); // -1 objects are passed by reference
console.log('hello world'.indexOf('o')); // 4
console.log([[1], [2], [3], [4]].indexOf([2])); // -1 array is passed by reference
console.log([[1], [2], [3], [4], myArray].indexOf(anotherArray)); //4

console.log(900.9 === 300.3 * 3);
console.log((300.3 * 3));
// fixed to two decimal, then convert string to Number
console.log(Number((300.3 * 3).toFixed(2)));
// get total 12 digits
console.log(Number((300.3 * 3).toPrecision(12)));
console.log(((300.3 * 10) * 3) / 10);

// Output:
//     false
//     900.9000000000001
//     900.9
//     900.9
//     900.9

var string1 = 'Tampa';
var string2 = string1;
string1 = 'Venice';

console.log(string2); // Tampa

var person1 = {
    name: 'Alex',
    age: 30
};

// both variables are referencing same objects
var person2 = person1;
person2.name = 'Kyle';
// { name: 'Kyle', age: 30 }

const data1 = 'Jordan Smith';

const data2 = [].filter.call(data1, function(elem, index) {
    return index > 6;
});

// only use 'read-only' methods: filter, forEach, map, some, every, etc. on string
// cannot use: push, pop, splice, shift, reverse, etc.

console.log(data2);

const a = {};
const b = { name: 'b' };
const c = { name: 'c' };

a[b] = 200;
// convert b object to a string
// a['[object Object]'] = 200

a[c] = 400;
// set again a['[object Object]'] = 400

console.log(a[b]);
// console.log(a['[object Object]']);

var x = 10;
function y() {
    // x() hoisted here
    // function x() {
    // }

    //resign x() to 100
    x = 100;
    return;
    function x() {}
}

y();

console.log(x);  // 10