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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops For Loops

Mahfuzur Rahman
Mahfuzur Rahman
3,204 Points
Posted by Mahfuzur Rahman
Mahfuzur Rahman
3,204 Points

purpose of html += '<div>' + i '</div>' ;

I understand what div is. But in the for loop how is the variable html changing? first html was an empty string. I don't understand how are we putting the values of 1 to 10 in it.

from my understanding variable html becomes == html+<div>+1 </div>== (when i=1)

Jake Cooper
Jake Cooper
Courses Plus Student 56,854 Points

+=

is for concatenation

 var a = "fuzz";
 a += "y";       // a -> "fuzzy"

=

is for assignment

 var a = "fuzz";
 a = "y";       // a -> "y"

1 Answer

Matthew Long
Matthew Long
28,407 Points
Matthew Long
Matthew Long
28,407 Points

You can always write out what a loop would be every time it runs.

var html = "";

for (var i = 0; i <= 10; i += 1) {
  html += "<div>" + i + "</div>";
}

When the above loop runs the first time the html is:

<div>1</div>

After it is run 10 times the html is:

<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
<div>5</div>
<div>6</div>
<div>7</div>
<div>8</div>
<div>9</div>
<div>10</div>

The reason it is a new <div> each time the loop is run is due to the += operator. It if was simply = then the html would be the following after being looped over 10 times:

<div>10</div>

Hopefully this clears things up for you.

Nicholas Wallen
Nicholas Wallen
12,278 Points
Nicholas Wallen
Nicholas Wallen
12,278 Points

That does help, A LOT.

Honestly, this was a very poorly taught video.