ELCT 5830 Network and Web Programming - Exercises 01

Lecture 01 JavaScript Basics

Q1.

Let X be a variable that stores a positive integer in which its last digit
is not zero. Write a segment of JS code to reverse its digits.

e.g. if X = 13579; X should become 97531.

function reverseDigit(x) {
    let res = 0;
    while (x != 0) {
        res = res * 10 + x % 10;
        x = (x / 10) | 0;
    }
    return res;
}

Q2.

Write a segment of JS code to make a DEEP copy of array “fruits” and sort the elements in the cloned arrayby “id” in ascending order.

const fruits = [
  {id:43, title:'Apple', price:12}, {id:21, title:'Banana', price:5},
  {id:13, title:'Orange', price:8}, {id:55, title:'Mango', price:15},
  {id:44, title:'Grape', price:10}, {id:6, title:'Peach', price: 14}
]

function deepCopy(obj) {
  return JSON.parse(JSON.stringify(obj));
}

function compare(a, b) {
  return a.id - b.id;
}

newArr = deepCopy(fruits).sort(compare)
console.log(newArr)

Q3.

Implement a function named “length” that takes one parameter and perform the followings:

• If the parameter is an array, return its length (# of elements)
• If the parameter is a string, return its length (# of characters)
• If the parameter is a number that is neither NaN nor Infinity, return the
  number of digits in its integer portion. (e.g., for -456.99, the integer
  portion is -456, so return 3)
• Otherwise, return 0

function length(x) {
    if (Array.isArray(x) || typeof(x) == "string") {
        return x.length;
    } else if (!isNaN(x) && x != Infinity) {
        return Math.abs(x | 0).toString().length;
    } else {
        return 0;
    }
}

Q4.

Implement a function that takes one parameter and returns true if the parameter is an object containing the following three properties: ‘foo’, ‘bar’, and ‘foo-bar’. Otherwise, the function returns false.

Please note that the value of the properties can be undefined.

function checkProperty(obj) {
    if (!obj) {
        return false;
    }
    return obj.hasOwnProperty("foo") && obj.hasOwnProperty("bar") && obj.hasOwnProperty("foo-bar");
}