In JavaScript, an expression is a piece of code that evaluates to a value. In this article, we will explore two categories of expressions: those with side effects and those that purely evaluate. By mastering these concepts with examples, you'll have a firm understanding of JavaScript expressions.
Let's start this article by discussing the categories of expression we have in javascript.
Categories of Expression
Expression with Side Effects
Expression that Purely Evaluates
Expression with Side Effects
The first category of expression is expression with side effects which involves modifying the program's state by assigning values to variables. Let's delve into an example:
x = 10;
In this expression, the assignment operator (=) assigns the value 10 to the variable x. The expression itself evaluates to 10.
Expression that Evaluates
The second category of expression is the one that purely evaluates and doesn't have any side effects. Let's consider the following example:
const result = 10 + 5;
console.log(result); // Output: 15
Now that we fully understand the two category of expression we have. We can now discuss the various types of expression we have in javascript
Types of Expression in Javascript
There are different types of expression
1. Arithmetic Expression.
2. String Expression.
3. Logical Expression.
4. Primary Expression.
1. Arithmetic Expression
Arithmetic expressions evaluate to numbers. They involve arithmetic operators such as addition ( + ), subtraction ( - ), multiplication ( * ), and division ( / ). Here are some examples:
10; // Evaluates to the number 10
10 + 5; // Evaluates to 15
10 - 5; // Evaluates to 5
10 * 2; // Evaluates to 20
2. String Expression
String expressions evaluate to strings. They can be string literals or involve string concatenation using the + operator. Here are some examples:
"hello"; // Evaluates to the string "hello"
"hello" + "world"; // Evaluates to the concatenated string "helloworld"
3. Logical Expression
Logical expressions evaluate to boolean values: either true or false. They involve comparison operators such as greater than (>), less than (<), and equal to (== or ===). Here are some examples:
20 > 10; // Evaluates to `true`
10 < 3; // Evaluates to `false`
true; // This is already evaluated and its value is `true`
"hello" === "world" // Evaluates to false
10 == "10" // Evaluates to true
10 === "10"//Evaluates to false
4. Primary Expression
Primary expressions refer to standalone expressions such as literal values, certain keywords, and variable values. They are constant or literal values. Here are some examples:
120; // A number literal
"hello"; // A string literal
Summary
In summary, expressions in JavaScript are powerful tools that produce values. They can have side effects, such as assigning values to variables, or purely evaluate to a value. We explored different types of expressions, including arithmetic expressions, string expressions, logical expressions, and primary expressions. Understanding expressions is essential for writing efficient and effective JavaScript code.
Feel free to experiment with the provided code examples to enhance your understanding of expressions in JavaScript.