Arrays of Objects

Objects are frequently stored in arrays. Let's create a few objects.

var tom = {
  name: "tom",
  job: "plumber"
}

var phil = {
  name: "phil",
  job: "teacher"
}

var susan = {
  name: "susan",
  job: "doctor"
}

Now we can store tom, phil, and susan in an array of people.

var people = [tom, phil, susan];

It is easy to iterate over an array of objects and print information to the console. Take note that this code is relatively easy to read.

for (var i = 0; i < people.length; i++) {
  var person = people[i];
  console.log(person.name + " is a " + person.job)
}

This for loop will print the following output to the console.

tom is a plumber
phil is a teacher
susan is a doctor

When the same data is stored in a nested array, the for loop is harder to read.

var peopleData = [
  ["tom", "plumber"],
  ["phil", "teacher"],
  ["susan", "doctor"]
]

for (var i = 0; i < peopleData.length; i++) {
  console.log(peopleData[i][0] + " is a " + peopleData[i][1]);
}

Arrays of objects are very common in JavaScript.

Question Click to View Answer

What does the following code print to the console?

var cat = {
  name: "garfield",
  mood: "blah"
}

var crazy = {
  name: "rambo",
  mood: "angry"
}

var random = [cat, crazy];

for (var i = 0; i < random.length; i++) {
  var thing = random[i];
  console.log(thing.name + " is " + thing.mood);
}

garfield is blah
rambo is angry

The for loop iterates through every element in the random array and prints a message to the console.

What does the following code print to the console?

var testOne = {
  score: 63,
  date: "2015-01-04"
}

var testTwo = {
  score: 85,
  date: "2015-02-07"
}

var testThree = {
  score: 74,
  date: "2015-05-10"
}

var tests = [testOne, testTwo, testThree];

var countPassingTests = 0;

for (var i = 0; i < tests.length; i++) {
  var test = tests[i];
  if (test.score > 65) {
    countPassingTests++;
  }
}

console.log(countPassingTests);

2

The for loop iterates over all the tests and increments the countPassingTests variable whenever the score is greater than 65. The countPassingTests variable is then printed to the console.
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