JavaScript vs. Ruby

After beginning JavaScript last Thursday, I’ve been thinking about the differences between this language and Ruby, whom I’ve gotten quite intimate with these last 7 weeks. Coming from Ruby, JavaScript isn’t all that different, yet the syntax is unfamiliar and some logic differs slightly.

typeof vs class

To determine what type of value something is (a number, a fixnum, a string, an Object, an array, etc), in JavaScript you write typeof and then then the object; in Ruby, you append .class to the end of the object.

=== vs ==

In JavaScript, the triple equals sign helps determine if two objects are the same exact object (having the same typeof and the same value). For example: 3 === 3 returns true In Ruby, that is accomplished through the double equals. (3 == 3 returns true)

JavaScript has its own double equals, which shouldn’t be confused with Ruby’s: double equals in JavaScript only determines if the values match. For example: "3" == 3 returns true

parseInt(); vs .to_i

In JavaScript, to turn a string “10” into the integer 10, you write parseInt("10");. In Ruby, you write "10".in_i.

Incrementing and Decrementing

To increment or decrement by 1 in JavaScript, you can write ++ or -- (for example, var x = 2; x++; returns 3. In Ruby, it’s x += 1. You can write this as well in JavaScript (which is useful if you want to increment with numbers other than 1), however, you have the handy ++ and -- as well.

Functions

Functions in JavaScript are the same as methods in Ruby. The syntax of declaring a function vs. declaring a method is slightly different. In Ruby, it’s :

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def hello
  puts "hello"
end

In JavaScript, the same logic can be written as:

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function hello() {
  console.log("hello");
}

Objects

Objects (similar to Ruby’s hash), declared as variables, are a way of organizing key/value pairs. For example, var cat = {color: "grey", name: "Spot", age: "12"}; To access the value of an associated key, you can call that on the variable name: cat.name returns "Spot". You can also easily delete a key/value pair by writing delete cat.name. To declare a new key/value pair, write: cat.gender = "male";. This appends this new data point to the end of the Object.

Arrays

Both Ruby and JavaScript have Arrays, which are more of less logically the same; however, the Object Array functions (JavaScript) and the Class Array methods (Ruby) have different syntax. For example, to find the index of an element in an array, in JavaScript you write arrayName.indexOf("element");. In Ruby, this is accomplished by array_name.index("element")

each

The method each in Ruby is a handy way of iterating through an array of elements in order to change or manipulate them. JavaScript as well as an each function that does the same thing; however, the syntax is slightly different:

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var arr = [1,2,3,4];
a.forEach(function(n) {
  console.log(n);
});

And in Ruby, the same is written as:

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arr = [1,2,3,4]

a.each {|n| puts n}

#or

a.each do |n|
    puts n
end

Falsey Values

One big difference between Ruby and JavaScript is the falsey-ness of certain values. Like in Ruby, null (in Ruby, it’s nil) and false will return false, however, some truthful values in Ruby will return false in JavaScript, like 0, empty strings (""), and undefined.

Object Oriented Programming

JavaScript, like Ruby, can be object-oriented, meaning that objects, their associated methods/functions, can be neatly contained. In JavaScript, a Prototype is much like Ruby’s Class. To create a new Prototype in JavaScript:

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function Cat(name, age, gender){
  this.name = name;
  this.age = parseInt(age);
  this.gender = gender;
  this.meow = function(){
    console.log("meow, my name is "+this.name+"! I am "+this.age+" years old.");
  };
};

var maruCat = new Cat("Maru", "6", "male");
maruCat.meow(); //meow, my name is Maru! I am 6 years old.

The maruCat object is considered a new instance of the Cat prototype. Prototype is essentially the same as Class in Ruby. Note that this in JavaScript is the same concept as self in Ruby.

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