Get Programming with JavaScript - Listing 8.04

Get Programming with JavaScript - Listing 8.04

Listing 8.04 - Using a variable as an index

var days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"];
var dayInWeek = 4;

console.log( days[dayInWeek] );
console.log( days[dayInWeek - 1] );

Further Adventures

Listing 8.04 - Using a variable as an index - Task 1

Change the value of the dayInWeek variable to display a different day.

var days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"];
var dayInWeek = 2;

console.log( days[dayInWeek] );
console.log( days[dayInWeek - 1] );

Listing 8.04 - Using a variable as an index - Task 2

Write a function that accepts a number for the day of the week to be displayed and returns the day as a string.
Assign the function to a getDay variable.

var getDay = function (dayNumber) {
    var days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"];
    return days[dayNumber - 1];
};

You could use Math.max and Math.min to make sure the dayNumber matches an element in the days array.

var getDay = function (dayNumber) {

    // dayNumber should be at least 1
    dayNumber = Math.max(1, dayNumber);

    // dayNumber must not exceed the number of days in the array
    dayNumber = Math.min(days.length, dayNumber);

    var days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"];
    return days[dayNumber - 1];   // the index is zero-based
};

Listing 8.04 - Using a variable as an index - Task 3

Call your function, passing it 4 as the day of the week.
Log the value it returns.

var getDay = function (dayNumber) {
    var days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"];
    return days[dayNumber - 1];
};

var dayInWeek = 4;

console.log( getDay(dayInWeek) );