<html>
<head>
<title> Colors </title>
</head>
<body>
<script type="text/javascript">
var a = parseInt(prompt("Enter R"));
var b = parseInt(prompt("Enter G"));
var c = parseInt(prompt("Enter B"));
document.body.style.backgroundColor=rgb(a,b,c);
</script>
</body>
</html>
Why doesn't the background color change according to the RGB values? What have I done wrong??
<html>
<head>
<title> Colors </title>
</head>
<body>
<script type="text/javascript">
var a = parseInt(prompt("Enter R"));
var b = parseInt(prompt("Enter G"));
var c = parseInt(prompt("Enter B"));
document.body.style.backgroundColor=rgb(a,b,c);
</script>
</body>
</html>
Why doesn't the background color change according to the RGB values? What have I done wrong??
Share Improve this question edited Jan 14, 2013 at 17:34 No Results Found 103k38 gold badges197 silver badges231 bronze badges asked Jan 14, 2013 at 17:03 Daniel VictorDaniel Victor 6692 gold badges7 silver badges11 bronze badges 3- 4 Look at the error console. – SLaks Commented Jan 14, 2013 at 17:30
- 1 what is the function rgb()? ;) – epascarello Commented Jan 14, 2013 at 18:26
- I just used like how it's used in HTML. :/ – Daniel Victor Commented Jan 14, 2013 at 19:30
7 Answers
Reset to default 53You need to use quotes:
document.body.style.backgroundColor = 'rgb(' + a + ',' + b + ',' + c + ')';
JS Fiddle demo.
Or:
document.body.style.backgroundColor = 'rgb(' + [a,b,c].join(',') + ')';
JS Fiddle demo.
Unquoted the JavaScript is passing the variables, as arguments, a,b and c to an undefined function called rgb(). As you're setting a CSS property you need to pass a string, hence the requirement of quoting.
Oh, and also you're using parseInt() which doesn't require a radix to be passed in, but it's better (and easier to avoid problems) if you do (the radix being the expected number-base):
var a = parseInt(prompt("Enter R"), 10) || 255,
b = parseInt(prompt("Enter G"), 10) || 255,
c = parseInt(prompt("Enter B"), 10) || 255;
JS Fiddle demo (In the demo I use 105 just so it's clear the default is being used if the cancel button is used).
And if someone hits 'cancel' on the prompt, you might want to supply a default argument to ensure that an actual colour-value is passed, since cancel otherwise, I think, evaluates to false (I'm assuming you'd prefer 255, but obviously adjust to taste).
You could also, of course, simply define a function:
function rgb(r,g,b) {
return 'rgb(' + [(r||0),(g||0),(b||0)].join(',') + ')';
}
var a = parseInt(prompt("Enter R"), 10),
b = parseInt(prompt("Enter G"), 10),
c = parseInt(prompt("Enter B"), 10);
document.body.style.backgroundColor = rgb(a,b,c);
JS Fiddle demo
And this approach has the (perhaps specious) benefit of allowing a custom default value to be used:
function rgb(r,g,b, def) {
def = parseInt(def, 10) || 0;
return 'rgb(' + [(r||def),(g||def),(b||def)].join(',') + ')';
}
var a = parseInt(prompt("Enter R"), 10),
b = parseInt(prompt("Enter G"), 10),
c = parseInt(prompt("Enter B"), 10);
document.body.style.backgroundColor = rgb(a,b,c,40);
JS Fiddle demo
References:
||(logicalOR) operator.Array.join().Element.style.parseInt().
Use quotes around the value
document.body.style.backgroundColor="rgb(" + a + "," + b + "," + c + ")";
rgb needs to be in quotation mark:
<html>
<head>
<title> Colors </title>
</head>
<body>
<script type="text/javascript">
var a = parseInt(prompt("Enter R"));
var b = parseInt(prompt("Enter G"));
var c = parseInt(prompt("Enter B"));
document.body.style.backgroundColor='rgb(' + a + ',' + b + ',' + c + ')';
</script>
</body>
</html>
jsFiddle http://jsfiddle.net/pduQ6/
You have no function called rgb(...)
I think you meant to do:
document.body.style.backgroundColor = "rgb(" + a + "," + b + "," + c + ");";
The problem is that the color needs to be a string:
var a = parseInt(prompt("Enter R"),10);
var b = parseInt(prompt("Enter G"),10);
var c = parseInt(prompt("Enter B"),10);
document.body.style.backgroundColor = "rgb(" + [a,b,c].join() + ")";
Demo
Setting a CSS property to any JavaScript variable requires the value to be passed inside quotation marks (as strings).
document.body.style.backgroundColor = 'red';
check out how we write red inside quotes, as it is a CSS property. Similarly, we write :
document.body.style.backgroundColor = 'rgb(x, y, z)';
This worked for me:
const red = 245;
const green = 128;
const blue = 56;
document.body.style.backgroundColor = `rgb(${red}, ${green}, ${blue})`;