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JavaScript Objects HTML DOM ObjectsJavaScript Comments
JavaScript comments can be used to make the code more readable.
JavaScript Comments
Comments will not be executed by JavaScript.
Comments can be added to explain the JavaScript, or to make the code more readable.
Single line comments start with //.
The following example uses single line comments to explain the code:
Example
// Write to a heading:
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
// Write to a paragraph:
document.getElementById("myP").innerHTML="This is my first paragraph.";
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
// Write to a paragraph:
document.getElementById("myP").innerHTML="This is my first paragraph.";
Try it yourself »
JavaScript Multi-Line Comments
Multi line comments start with /* and end with */.
The following example uses a multi line comment to explain the code:
Example
/*
The code below will write
to a heading and to a paragraph,
and will represent the start of
my homepage:
*/
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";
The code below will write
to a heading and to a paragraph,
and will represent the start of
my homepage:
*/
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";
Try it yourself »
Using Comments to Prevent Execution
In the following example the comment is used to prevent the execution of one of the codelines (can be suitable for debugging):
Example
//document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";
document.getElementById("myP").innerHTML="This is my first paragraph.";
Try it yourself »
In the following example the comment is used to prevent the execution of a code block (can be suitable for debugging):
Example
/*
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";
*/
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";
*/
Try it yourself »
Using Comments at the End of a Line
In the following example the comment is placed at the end of a code line:
Example
var x=5; // declare x and assign 5 to it
var y=x+2; // declare y and assign x+2 to it
var y=x+2; // declare y and assign x+2 to it
Try it yourself »
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