Help Need with Javascript

[King_Jay16]

Need help writing an array in Javascript.


I need to create an array of size 20, in order to populate the array i have to do some addition.

The values in slots [0] and [1] will be added and saved in slot [2], then slot [1] and [2] will be added to fill slot [3].

This is what I have so far

<script type="text/javascript">
<!--
var myArray = new Array(20);

myArray[0] = "2";
myArray[1] = "1";
 
 for (var i = 0; i < myArray.length-1; i++)
{
   for (var j = 1; j < myArray.length-1; j++)

   {
     for (var x = 2; x < myArray.length; x++)

{
     myArray[x] = myArray[i] + myArray[j];


document.write( +myArray[x] );
}
}
}
//-->
</script>

[Arch_Angel]

Haven't tested this and I haven't coded in javascript in a while so I am a bit rusty. But see if this will work.

<script type="text/javascript">
<!--
var myArray = new Array(20);

myArray[0] = "2";
myArray[1] = "1";
var i = 0;
var j = 1;
for (var x = 2; x < myArray.length; x++)
{
    myArray[x] = myArray[i] + myArray[j];
    document.write(myArray[x]);
    i++;
    j++;
}

//-->
</script>

[King_Jay16]

Haven't tested this and I haven't coded in javascript in a while so I am a bit rusty. But see if this will work.

<script type="text/javascript">
<!--
var myArray = new Array(20);

myArray[0] = "2";
myArray[1] = "1";
var i = 0;
var j = 1;
for (var x = 2; x < myArray.length; x++)
{
    myArray[x] = myArray[i] + myArray[j];
    document.write(myArray[x]);
    i++;
    j++;
}

//-->
</script>

just tried it but only gives a repetition of 21121211211212112121121121211211212112121121121211 21211211212112112121121211211212112112121121211211 212


http://writecodeonline.com/javascript/

[Arch_Angel]

just tried it but only gives a repetition of 21121211211212112121121121211211212112121121121211 21211211212112112121121211211212112112121121211211 212


http://writecodeonline.com/javascript/

Oops. Remove the quotes around the 2 and the 1. What javascript does with the values depends on how you store the values.
You stored them as strings (the quotes around them), so when you try to add them, javascript puts them together to get 21.

Remove the quotes and it will treat them as numbers.

<script type="text/javascript">
<!--
var myArray = new Array(20);

myArray[0] = 2;
myArray[1] = 1;
var i = 0;
var j = 1;
for (var x = 2; x < myArray.length; x++)
{
    myArray[x] = myArray[i] + myArray[j];
    document.write(myArray[x]);
    i++;
    j++;
}

//-->
</script>

[King_Jay16]

Oops. Remove the quotes around the 2 and the 1. What javascript does with the values depends on how you store the values.
You stored them as strings (the quotes around them), so when you try to add them, javascript puts them together to get 21.

Remove the quotes and it will treat them as numbers.

<script type="text/javascript">
<!--
var myArray = new Array(20);

myArray[0] = 2;
myArray[1] = 1;
var i = 0;
var j = 1;
for (var x = 2; x < myArray.length; x++)
{
    myArray[x] = myArray[i] + myArray[j];
    document.write(myArray[x]);
    i++;
    j++;
}

//-->
</script>

Thanks!!!


i figured out another way as well

<script type="text/javascript"> 
<!--
var myArray = new Array(20);

myArray[0] = "2";
myArray[1] = "1";
 

for (var i = 2; i < myArray.length-1; i++)
{

   myArray[i] = parseInt(myArray[i-1]) + parseInt(myArray[i-2]);

   document.write( +myArray[i] + ','  );
}
//-->
</script>

Thanks again... first time with Javascript so was aplying C/C++/C# knowledge...



OT: We need a rep system here!!!

[Arch_Angel]

Thanks!!!

i figured out another way as well

Yes that will work, but you're making extra calls to the function parseInt(), to convert the string to an integer.
Instead, just remove the quotes around the 2 and the 1 and you wouldn't have to use parseInt(). Javascript will treat it as an integer.

myArray[0] = 2;
myArray[1] = 1;
...
...
myArray[i] = myArray[i-1] + myArray[i-2];
...

In a small script like this, the small overhead of extra calls to parseInt() when it's not needed, won't make a huge difference. But better start coding efficiently now instead of later when your page starts to take some time to load.

[King_Jay16]

Yes that will work, but you're making extra calls to the function parseInt(), to convert the string to an integer.
Instead, just remove the quotes around the 2 and the 1 and you wouldn't have to use parseInt(). Javascript will treat it as an integer.

myArray[0] = 2;
myArray[1] = 1;
...
...
myArray[i] = myArray[i-1] + myArray[i-2];
...

In a small script like this, the small overhead of extra calls to parseInt() when it's not needed, won't make a huge difference. But better start coding efficiently now instead of later when your page starts to take some time to load.

i agree with you on that, thank you!!

[xegnma]

Looks like you're trying to generate Fibonacci's Sequence. You could try the following code I cobbled together. Its a cleaner implementation with the algorithm contained within a function:

// define Fibonacci function    
function fibonacci(length) {
    if (length < 2) throw new Error("length must be greater than or equal to 2");
    
    var sequence = [1,1]; // declare and initialize an array
    var i = 2;
    
    while(i < length){
        sequence.push(sequence[i-2] + sequence[i-1]);
        i++;
    }
    
    return sequence;
}
    
// generate an array with the first 20 numbers in the Fibonacci sequence
var fib_20 = fibonacci(20);
document.write(fib_20);

I posted this code up on jsdo.it. So you can try it out for yourself at the following link : Fibonacci Sequence

[King_Jay16]

Looks like you're trying to generate Fibonacci's Sequence. You could try the following code I cobbled together. Its a cleaner implementation with the algorithm contained within a function:

// define Fibonacci function    
function fibonacci(length) {
    if (length < 2) throw new Error("length must be greater than or equal to 2");
    
    var sequence = [1,1]; // declare and initialize an array
    var i = 2;
    
    while(i < length){
        sequence.push(sequence[i-2] + sequence[i-1]);
        i++;
    }
    
    return sequence;
}
    
// generate an array with the first 20 numbers in the Fibonacci sequence
var fib_20 = fibonacci(20);
document.write(fib_20);

I posted this code up on jsdo.it. So you can try it out for yourself at the following link : Fibonacci Sequence

Yup that is what I am generating, thanks for the additional post