Question

Why comments are used within JavaScript programs? (i) To tell the browser there is HTML in our JavaScript code. (ii) Because HTML does not have its own command for comments. (iii) To explain what a script does. (iv) None of the above.

Answer 1

Answer:

Hey mate...

Explanation:

JavaScript comments can be used to explain JavaScript code, and to make it more readable.

JavaScript comments can also be used to prevent execution, when testing alternative code.

Single Line Comments

Single line comments start with //.

Any text between // and the end of the line will be ignored by JavaScript (will not be executed).

This example uses a single-line comment before each code line:

Example

// Change heading:

document.getElementById("myH").innerHTML = "My First Page";

// Change paragraph:

document.getElementById("myP").innerHTML = "My first paragraph.";

This example uses a single line comment at the end of each line to explain the code:

Example

var x = 5; // Declare x, give it the value of 5

var y = x + 2; // Declare y, give it the value of x + 2

Multi-line Comments

Multi-line comments start with /* and end with */.

Any text between /* and */ will be ignored by JavaScript.

This example uses a multi-line comment (a comment block) to explain the code:

Example

/*

The code below will change

the heading with id = "myH"

and the paragraph with id = "myP"

in my web page:

*/

document.getElementById("myH").innerHTML = "My First Page";

document.getElementById("myP").innerHTML = "My first paragraph.";

It is most common to use single line comments.

Block comments are often used for formal documentation.

Using Comments to Prevent Execution

Using comments to prevent execution of code is suitable for code testing.

Adding // in front of a code line changes the code lines from an executable line to a comment.

This example uses // to prevent execution of one of the code lines:

Example

//document.getElementById("myH").innerHTML = "My First Page";

document.getElementById("myP").innerHTML = "My first paragraph.";

This example uses a comment block to prevent execution of multiple lines:

Example

/*

document.getElementById("myH").innerHTML = "My First Page";

document.getElementById("myP").innerHTML = "My first paragraph.";

*/

Answer 2

Comments are used within JavaScript programs i)to tell the browser there is HTML in our JavaScript code.

Explanation:  

Comments on a single line begin with /.

JavaScript must ignore all text between / and the end of the line (not executed).

This example uses an individual line before each line of code:

// Change heading:

document.getElementById("myH").innerHTML = "My First Page";

// Change paragraph:

document.getElementById("myP").innerHTML = "My first paragraph.";