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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops The Refactor Challenge Solution

Posted by Eni Begotaraj
Eni Begotaraj
13,723 Points

Use of comma inside ' , ' Why the preview doesn't show if i remove it ??

var html = ' '; var red; var green; var blue; var rgbColor;

for ( var i = 1; i <= 100; i +=1) { red = Math.floor(Math.random() * 256 ); green = Math.floor(Math.random() * 256 ); blue = Math.floor(Math.random() * 256 ); rgbColor = 'rgb(' + red + ',' + green + ',' + blue + ')'; html += '<div style="background-color:' + rgbColor + '"></div>'; } document.write(html);

rgbColor = 'rgb(' + red + ',' + green + ',' + blue + ')';

On the line of code above a coma is used inside ' , ' If i remove it, and try to preview the code nothing shows. I thought an empty space between ' ' was supposed to be space . For what does the comma stands for?

1 Answer

Christian Andersson
Christian Andersson
8,712 Points

You are programmatically adding background-color (a CSS property) to a div element. You can define a background-color in several ways. A common way is with a hexadecimal value (e.g background-color: #ffab67). However, you can also define it with a decimal value with (e.g background-color: rgb(255,0,255);).

Here, the comma is used to separate the red, green and blue values from eachother. If you didn't need to do this, and you had rgb(2550255) that could be red:25, blue:50 and green:255 or red:255, blue:0 and green:255. So to make it clear, the commas are used to separate the different values.

So if you remove a comma, this becomes an invalid CSS property, and no color is added.

Eni Begotaraj
Eni Begotaraj
13,723 Points

Thank you Christian. It was very clear.