Using Indexed Arrays

You can practice working with arrays interactively using the web browser Console window.

Lesson Setup Instructions

This lesson's activities uses the console interactive mode.

Steps:

  1. Open in the web browser the console.html file found in the completed folder.

    Alternatively any open web page can be used.

  2. Open the Console window in the web developer tools.

    For details see the Using Web Browser Developer Tools to Learn lesson in the Getting Started section for interactively accessing the Chrome Console window.

1. Lab: The Confucius Says array.

  1. In the Console window enter the following …

    var quotes = []
    quotes
    quotes.length
    quotes.push("Be not ashamed of mistakes and thus make them crimes.")
    quotes
    quotes.length

    Declare quotes array and assign empty list. Use push method to add one item.

  2. In the Console window enter the following …

    quotes.push("Before you embark on a journey of revenge, dig two graves.");
quotes.push("Everything has its beauty but not everyone sees it.");
quotes.push("Forget injuries, never forget kindnesses.");
quotes.push("He who will not economize will have to agonize.");
quotes.push("I hear and I forget. I see and I remember. I do and I understand");
quotes.push("Ignorance is the night of the mind, but a night without moon and star.");
quotes.push("It does not matter how slowly you go so long as you do not stop.");
quotes.push("Our greatest glory is not in never falling, but in getting up every time we do.");
quotes.push("Learning without thought is labor lost; thought without learning is perilous.");
quotes.push("Real knowledge is to know the extent of one's ignorance.");
quotes.push("Choose a job you love and you will never have to work a day in your life.");

    Use the push method to add 11 items to the quotes array.

  3. Expand the array output line.

    The array line in the console window expanded to see items and the length property.

  4. In the Console window enter the following …

    quotes.length
    quotes[0]
    quotes[4]
    quotes[12]

    Use the push method to add 11 items to the quotes array.

  5. In the Console window enter the following …

    var randomQuoteIndex = Math.floor(Math.random() * quotes.length + 1)
    randomQuoteIndex
    quotes[randomQuoteIndex - 1]
    randomQuoteIndex = Math.floor(Math.random() * quotes.length + 1)
    randomQuoteIndex

    Generating random indices to reference items in the quotes array.

    Your randomQuoteIndex values may be different.

2. Lab: The Scores array.

  1. In the Console window enter the following …

    var score1 = Math.floor(Math.random() * 100 + 1)
    score1
    var score2 = 55
    score2
    var scores = [score1, score2, 75]
    scores

    Declare scores array and assign value using 2 number variables and a literal numbers.

  2. In the Console window enter the following …

    scores.push(Math.floor(Math.random() * 100 + 1));
scores.push(Math.floor(Math.random() * 100 + 1));
scores.push(Math.floor(Math.random() * 100 + 1));
scores.push(Math.floor(Math.random() * 100 + 1));
scores.push(Math.floor(Math.random() * 100 + 1));
scores.push(Math.floor(Math.random() * 100 + 1));
scores.push(99);

    Use push method to add 7 more items to scores array.

  3. In the Console window enter the following …

    scores[2]
    scores[2] = 25
    scores[2]
    scores[scores.length - 1]
    scores[scores.length - 1] = (score1 + score2) / 2
    scores[scores.length - 1]
    scores

    Use push method to add 7 more items to scores array.

  4. In the Console window enter the following …

    var currentIndex = 0;
    scores[currentIndex];
    scores[currentIndex + 2];
    scores[currentIndex + 12];

    Using a variables and expressions for scores array index references.

Complete and Continue