JavaScript - Beginner Help Please

hello!
i have a problem:
i want to change the height of my side bar as long as the text in the center of page long,
it means when I have for ex 3 news in a page the side bar which have a background color must be increase to fit the long of text(3 news).

i think it will do by javascript but i'm not sure!

i my question isn't clear please tell me to explane more i really need it,

I am very new to JavaScript and I am currently following the Eloquent JavaScript book online.
On one of the exercises, we are told to make a function that returns the range of the inputs in an array.
I tried this code below but it doesn't seem to work. The problem seems to be in the "If" function because if I change the condition to (start < end) it seems to work.
Can someone please explain to me why this is?


function range (start, end) {
var j = [];
if (start > end) {
for (i = start; i <= end; i++) {
j.push(i); }
} else {
for (i = start; i >= end; i--) {
j.push(i); }
}
return j;
}

console.log(range(10, 2));
console.log(range(2, 10));





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01-26-2015, 08:49 PM #2
Labrar View Profile View Forum Posts

New Coder Join Date Jun 2008 Posts 65 Thanks 0 Thanked 12 Times in 12 Posts

Why you do not use something like this

var range = function(start, end, step) {
var range = [];
var typeofStart = typeof start;
var typeofEnd = typeof end;

if (step === 0) {
throw TypeError("Step cannot be zero.");
}

if (typeofStart == "undefined" || typeofEnd == "undefined") {
throw TypeError("Must pass start and end arguments.");
} else if (typeofStart != typeofEnd) {
throw TypeError("Start and end arguments must be of same type.");
}

typeof step == "undefined" && (step = 1);

if (end < start) {
step = -step;
}

if (typeofStart == "number") {

while (step > 0 ? end >= start : end <= start) {
range.push(start);
start += step;
}

} else if (typeofStart == "string") {

if (start.length != 1 || end.length != 1) {
throw TypeError("Only strings with one character are supported.");
}

start = start.charCodeAt(0);
end = end.charCodeAt(0);

while (step > 0 ? end >= start : end <= start) {
range.push(String.fromCharCode(start));
start += step;
}

} else {
throw TypeError("Only string and number types are supported");
}

return range;

}


Thats pretty similar to php range





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01-26-2015, 09:25 PM #3
Old Pedant View Profile View Forum Posts

Supreme Master coder! Join Date Feb 2009 Posts 28,310 Thanks 82 Thanked 4,754 Times in 4,716 Posts

Ignore Labrar's ridiculously complicated answer to a very simple problem.

Instead look CAREFULLY at this code: Code:

if (start > end) {
    for (i = start; i <= end; i++) {

Let's use your first example, where you call range(10, 2)

So start is 10. And end is 2.

So you get to if ( start > end ) and JavaScript executes that as if ( 10 > 2 )

Indeed, 10 *IS* greater than 2, yes?

SO you the go execute the NEXT line: for (i = start; i <= end; i++)

Which, of course, JavaScript then executes as for (i = 10; i <= 2; i++)

But then 10 is *IMMEDIATELY* <= 2. So the for loop NEVER RUNS.

All you need to do to fix your code is change Code:

if (start > end) {

into Code:

if (start < end) {

PRESTO!

**********

The tiniest bit of debugging using your JavaScript debugger would have found this. But also just learning to THINK like the computer would help. Actually run the code in your head, using your example numbers, and you'd see where you went wrong.

Hi there, im wondering if you can help me i need help in finding javascript resources to build my skills and knowledge of Jscript because im a beginner.

Please help

is this code right its supposed to be a code that prompts the user for a number less than 100 and outputs only odd numbers less than or equal to the number entered by the user.for example if a user eneters the number 10 you should display 1,3,5,7,9 to the browser window?...im not sure if i have done it right..i gave it a go though!


var input = prompt("Enter a number less than 100:", "10");
if( input <= 100){

nbsp; for (var i = 1, i <= input, i++2){
nbsp; document.write(i", ");
nbsp; }

}else{
nbsp; alert(input + " is not less than 100!");
}

I'm trying to get this simple (not to me) ascii animation going and firebug is giving me an error saying "document.getElementById("frameArea") is null. I've got an element named frameArea and I wonder if it's buried too deep.

I don't really understand this code which I admit is a big part of my problem. I have seen what it is supposed to do, which is play a simple animation. Will someone please help me decipher what this code is saying?


Code:

<html>

<head>
  <title>Animation</title>
  
  <script type="text/javaScript">
 function playAnimation()
      {
       frameStr = document.getElementById("frameArea").value;
       if(frameStr.indexOf("\r\n") != -1)
       {
        frameSeq = frameStr.split("=====\r\n");
       }
       else
       {
        frameSeq = frameStr.split("=====\n");
       }
       currentFrame = 0;
       showNextFrame();
       }
      function showNextFrame()
       {
       document.getElementById("displayArea").value = frameSeq[currentFrame]; 
       currentFrame = (currentFrame+1)% frameSeq.length;
       timer = setTimeout("showNextFrame();", 250);
       }
	</script>
</head>

<body>
  <div style="text-align:left">
  
  <h1>My Animation</h1>
   
  <hr />
  
  <form name="animationForm">
 
    <table>
    <tr><td align="center"><b>Enter frames below separated by "====="</b>
        <td>
        <td align="center">

    <tr><td><textarea name="frameArea" rows=12 cols=35 wrap="virtual"></textarea> </td>
        <td align="center"> 
		<br />
            <input type="button" value="Play --->" onclick="playAnimation()">
		</td>
        <td><textarea name="displayArea" rows=12 cols=35 wrap="virtual"></textarea> </td>
    </tr>
    </table>

  </form>
  </div>
</body>
</html>