Strings, Arrays and Objects


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Strings

The Javascript String is immutable, but it includes various accessor methods such as substring and indexOf.


// Strings are created with ' or ".
'abc';
"Hello, world";

// Strings are concatenated with +
"Hello " + "world!"; // = "Hello world!"

// Other types automatically convert to strings for concatenation
"Hello " + 10; // = "Hello 10"

// Strings can be alphabetically compared with < and >
"a" < "b"; // = true

// Access specific characters with charAt
"Hello".charAt(0); // = "H"
//...or use substring to get larger pieces
"Hello world".substring(0, 5); // = "Hello"

//length is a property, so don't use ()
"Hello".length; // = 5

//Print to the console (for debugging)
console.log("Hello"); //  Hello

// Print to output in these challenges 
print("hello");  // Hello

Arrays

Arrays are ordered lists of values of any type. They share many methods with Strings.

var myArray = ["Hello", 42, true];

// Their members can be accessed using the square-brackets subscript syntax.
// Array indices start at zero.
myArray[1]; // = 42

// Use push to add to an Array
myArray.push("World");

//or Add/modify at a specific index:
myArray[1] = 2;

myArray; // = ["Hello", 2, true, "World"]

myArray.length; // = 4

Objects / Hashes

A JavaScript object is an unordered collection of unique keys mapped to specific values. In this way, they're similar to the Hashes or dictionaries of other languages.


var myObj = {key1: "Hello", key2: "World"};

// Keys are strings, but quotes aren't required if they're a valid
// JavaScript identifier. Values can be any type.
var myObj = {myKey: "myValue", "another key": 20};

// Object attributes can be accessed using the subscript syntax,
myObj["another key"]; // = 20

// ... or using the dot syntax, provided the key is a valid identifier.
myObj.myKey; // = "myValue"

// Objects are mutable; values can be changed and new keys added.
myObj.myThirdKey = true;
myObj["key4"] = 40;

myObj; // =  Object {myKey: "myValue", another key: 20, myThirdKey: true, key4: 40}

// Accessing a key that's not there will return undefined
myObj.key5; // = undefined

Javascript objects can also have associated functions, which will be covered soon.

Challenge

What will the following code return?

 "L" + 33 + "t"

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Challenge

For each word, you are given, print "Hello {word}!".
(Replace {word} with the given word).

Note: In these challenges, use print() to print to output.

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Challenge

Using the same syntax as above, create a car object with a "green" color and a speed of 0.

(Remember to use var and a ; at the end)

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