CoffeeScript - Operators and Aliases

CoffeeScript Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical functions. Let us take a simple expression 4 + 5 is equal to 9. Here 4 and 5 are called operands and ‘+’ is called the operator.

The operators provided by CoffeeScript are same as in JavaScript except a few differences. There are some problematic operators in JavaScript. CoffeeScript either removed them or modified their functionality and it also introduced some new operators.

Following is the list of operators supported by CoffeeScript.

• Arithmetic Operators
• Comparison Operators
• Logical (or Relational) Operators
• Assignment Operators

CoffeeScript Aliases

In addition to operators, CoffeeScript also provides aliases. CoffeeScript provides aliases to various operators and symbols in order to make your CoffeeScript code readable and more user friendly.

Let us have a look at all the operators and aliases of CoffeeScript one by one.

Arithmetic Operators

CoffeeScript supports the following arithmetic operators. Assume variable A holds 10 and variable B holds 20, then −

Show Examples

Comparison Operators

JavaScript supports the following comparison operators. Assume variable A holds 10 and variable B holds 20, then −

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Following table shows the aliases for few of the Comparison operators. Suppose A holds 20 and variable B holds 20.

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Logical Operators

CoffeeScript supports the following logical operators. Assume variable A holds 10 and variable B holds 20, then −

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The following table shows the aliases for some of the logical operators. Suppose X holds true and variable Y holds false.

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Bitwise Operators

CoffeeScript supports the following bitwise operators. Assume variable A holds 2 and variable B holds 3, then −

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Assignment Operators

CoffeeScript supports the following assignment operators −

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Note − Same logic applies to Bitwise operators so they will become like <<=, >>=, >>=, &=, |= and ^=.

Equality Operator in CoffeeScript

While working with JavaScript, you will encounter two types of equality operators == and ===.

The == operator in JavaScript is type coercive, i.e., if the types of the two operands in an operation are different, then the data type of one of the operator is converted into other and then both are compared.

CoffeeScript avoids this undesirable coercion, it compiles the == operator in to the strict comparison operator of JavaScript ===.

If we compare two operands using ===, then it returns true, only if both the value and datatypes of them are equal, else it returns false.

Example

Consider the following example. Here we have two variables a and b. a holds the value 21 of integer type and b holds the same value, but it is of string type. In CoffeeScript, when we compare a and b, the result will be false. (Since the == operator of CoffeeScript is converted to === operator of JavaScript)

a=21
b="21"
result = 21=='21'
console.log result

On compiling, the above CoffeeScript produces the following JavaScript

// Generated by CoffeeScript 1.10.0
(function() {
  var a, b, result;
  
  a = 21;
  
  b = "21";
  
  result = a === b;
  console.log(result);
}).call(this);

On executing, it produces the following output.

false

The existential Operator

CoffeeScript provides a new operator known as existential operator to verify the existence of a variable. It is denoted by ?. Unless a variable is null or undefined, the existential operator returns true.

Example

Given below is an example of the existential operator. Here we have three variables, namely name, age, and subject and we are verifying the existence of the variables name and phone using existential operator.

name="Ramu"
age=24
subject="Engineering"
verify_name = name?
verify_phone = phone?
console.log verify_name
console.log verify_phone

On compiling, this will generate the following JavaScript code.

// Generated by CoffeeScript 1.10.0
(function() {
  var age, name, subject, verify_name, verify_phone;
  name = "Ramu";
  age = 24;

  subject = "Engineering";
  verify_name = name != null;
  verify_phone = typeof phone !== "undefined" && phone !== null;
  console.log(verify_name);
  console.log(verify_phone);

}).call(this);

If we execute the above CoffeeScript file, it produces the following output.

true
false

Note − We have an accessor variant of the existential operator ?. We can use it instead of the . operator to find out the null references.

Chained Comparisons

As in Python, we can use a chain of comparison operators in a single expression in CoffeeScript.

Example

Following is an example of using chained comparison.

score = 70
passed = 100 > score > 40

console.log passed

On compiling, the example CoffeeScript gives you the following JavaScript code.

// Generated by CoffeeScript 1.10.0
(function() {
  var passed, score;

  score = 70;

  passed = (100 > score && score > 40);

  console.log(passed);

}).call(this);

If you execute the above CoffeeScript code, it produces the following output.

true

Note − CoffeeScript removes the ternary operator; instead of it, we can use the inline if statement.

CoffeeScript Aliases

In general, CoffeeScript provides aliases to various operators and symbols in order to make your CoffeeScript code readable and more user friendly. Following are the aliases provided by CoffeeScript.

Example

The following example shows how to use aliases in CoffeeScript −

a=21; b=21

x = true; y = false

console.log a is b

console.log a isnt b

console.log x and y

console.log x or y

console.log yes or no

console.log on or off

console.log a**b

console.log a//b

console.log a%%b

On compiling the above example, it gives you the following JavaScript code.

// Generated by CoffeeScript 1.10.0
(function() {
  var a, b, x, y,
    modulo = function(a, b) { return (+a % (b = +b) + b) % b; };

  a = 21;

  b = 21;

  x = true;

  y = false;

  console.log(a === b);

  console.log(a !== b);

  console.log(x && y);

  console.log(x || y);

  console.log(true || false);

  console.log(true || false);

  console.log(Math.pow(a, b));

  console.log(Math.floor(a / b));

  console.log(modulo(a, b));

}).call(this);

If you execute the above CoffeeScript file, it produces the following output −

true
false
false
true
true
true
5.842587018385982e+27
1
0