JavaScript_Fundamentals_Objects.js

//Task 1 Hello, Object
// Write the code, one line for each action:

// Create an empty object user.
let user = {};

// Add the property name with the value John.
user.name = "John";

// Add the property surname with the value Smith.
user.surname = "Smith";

// Change the value of the name to Pete.
user.name = "Pete";

// Remove the property name from the object.
delete user.name;

//Task 2 Check For Emptiness
//Write the function isEmpty(obj) which returns true if the object has no properties, false otherwise.
function isEmpty(obj) {
    for (let key in obj) {
        if (obj.hasOwnProperty(key)) {
            return false;
        }
    }
    return true;
}

//Task 3 Sum Object Properties
//We have an object storing salaries of our team:
let salaries = {
    John: 100,
    Ann: 160,
    Pete: 130
};
//Write the code to sum all salaries and store in the variable sum. Should be 390 in the example above.
// If salaries is empty, then the result must be 0.
    let sum = 0;
    for (let key in salaries) {
            sum += salaries[key];
        }
    alert(sum); 

    //Task 4 Multiply Numeric Property Values By 2
    // Create a function multiplyNumeric(obj) that multiplies all numeric property values of obj by 2.
    //beforre the call
    let menu = {
        width: 200,
        height: 300,
        title: "My menu"
    };

    multiplyNumeric(menu);

    //after the call
    menu = {
        width: 400,
        height: 600,
        title: "My menu"
    };

    //Please note that multiplyNumeric does not need to return anything. It should modify the object in-place. 
    // P.S. Use typeof to check for a number here.

    function multiplyNumeric(obj) {
        for (let key in obj) {
            if (typeof obj[key] === 'number') {
                obj[key] *= 2;
              }
        }
    }