Write a Program to Check The Given String is Comment or Not using JavaScript | Compiler Design

What is Comments and Types of Comments in Programming Languages with Examples:

Comments play a significant role in delivering meaningful messages within code. They provide valuable information, warnings, or suggestions to help end-users interpret the code more easily. 

There are two primary types of comments commonly used in programming:

1) Single-line  Comments: These comments start with double forward slashes (//).

They are used to annotate a single line of code or provide a brief explanation of its purpose. Single-line comments are ignored by the compiler or interpreter and are purely meant for human readers.

 Single-line comments Example:

// This is a single-line comment
var age = 25; // Initializing a variable

2) Multi-line Comments: Also known as block comments, they start with a forward slash and asterisk (/) and end with an asterisk and forward slash (/).

Multi-line comments can span across multiple lines and are commonly used to provide more extensive explanations or to temporarily disable a block of code.

Multi-line comments can span across multiple lines and are commonly used to provide more extensive explanations or to temporarily disable a block of code.

Multi-line Comments Example:

/*
This is a multi-line comment
that provides detailed information
about the code.
*/

/* This is another way
   to write a multi-line comment */

By using comments effectively, programmers can improve code readability, facilitate collaboration among team members, and make the codebase more maintainable and understandable in the long run.

Program to Check The Given String is Comment or Not using   JavaScript :

const detectComment = expressions => {  
    for(let comment of expressions){
        let result = (comment.startsWith("/*") && comment.endsWith("*/")) 
                  ? "It is multi-line comment"
                  : comment.startsWith("//")? "It is a single line comment"
                  : "It is not a comment";
        console.log(`${comment} => ${result}`);
    } 
}

 
//takes input and runs only in browser console
let line = prompt("Enter the number of lines to write code:");
let expressions = [];

for(let i=0;i<line;i++) {
    expressions.push(prompt(`Enter the expression of line ${i+1}:`));
}

detectComment(expressions);

This JavaScript code snippet demonstrates a function called detectComment that detects whether a given set of expressions are comments or not. Let's go through the code step by step:

The detectComment function takes an array of expressions as input. This array contains the lines of code or expressions that need to be checked for comments.

Inside the function, a for...of loop is used to iterate over each comment in the expressions array.

For each comment, an if statement is used to check whether it starts with "/*" and ends with "*/". If this condition is true, the comment is identified as a multi-line comment.

If the condition in the previous step is false, the if statement checks whether the comment starts with "//". If this condition is true, the comment is identified as a single-line comment.

If both conditions in steps 3 and 4 are false, the comment is identified as not being a comment.

Based on the identification result, a message is assigned to the result variable.

Finally, using console.log, the code displays the original comment along with the corresponding result message.

The code snippet also provides an example of how to use the detectComment function by taking user input using prompt. The user is asked to enter the number of lines of code (line variable), and then prompted to enter each expression or line of code. These expressions are stored in the expressions array, which is then passed to the detectComment function.

The detectComment function then checks each expression and outputs the result using console.log.

Input/Output:

This code can be run in a browser console or an environment that supports the prompt function. It allows users to enter their own code expressions and see the comment detection results.

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