Peter Nyboer

Is it possible to create a javascript array with an arbitrary name on the fly? I don't quite see how I can do this.

the goal is to create a function that takes a path to a folder, iterates through the folder and 3-5 layers of subfolders, and puts the paths of all files in those folders into an array. Ideally, this array could be made on the fly, so I don't have to preallocate a LOT of arrays at the start of my js code. That would be messy, not to mention limiting!

to show you how much I don't understand, here is a code snippet that of course doesn't work:

the message "newone jones 2" just adds the value 2 to the array "v".

Is it possible to create a javascript array with an arbitrary name on the fly?  I don't quite see how I can do this.  

the goal is to create a function that takes a path to a folder, iterates through the folder and 3-5 layers of subfolders, and puts the paths of all files in those folders into an array.  Ideally, this array could be made on the fly, so I don't have to preallocate a LOT of arrays at the start of my js code.  That would be messy, not to mention limiting!

function newone(v,a)
{
	v = new Array();
	v[0]=a;
}

create-array-dynamically

maybe you could do something with a "2 dimensional" array.

Then every time you need to create a new array you could just keep appending new arrays in v

thanks andrew, that seems to work nicely!

    post(n," :",temp[0],temp[1],temp[2],"n");    

function makenew(x)
{
	v[x] = new Array();
}

function vary(x,n,b)
{
	var jones = new Array();
	jones = v[x];
	jones[n] = b;

function dump(n)
{
	var temp = new Array();
	temp = v[n];
	post(n," :",temp[0],temp[1],temp[2],"n");	
}

    if(eval("!" + a[0])) // test for non-existence

        eval(a[0] + " = [" + a.slice(1) + "]");

    else if(eval("typeof(" + a[0] + ".slice) == "function"")) // test for array

        eval(a[0] + " = " + a[0] + ".concat(" + a.slice(1) + ")");

        post(a[0] + ": not an arrayn");

    if(eval("typeof(" + a[0] + ".slice) == "function"")) // test for array

        post("array " + aname + ": clearedn");

but I guess what I meant is how can i initialize an array dynamically. These are for manipulation of an existing array, correct?

cool...the eval function is new to me!  
but I guess what I meant is how can i initialize an array dynamically.  These are for manipulation of an existing array, correct?

eval() can do anything you want dynamically. this is the big bonus of 

an interpreted language. go nuts. i sure do. there are user-code 

eval() can do anything you want dynamically.  this is the big bonus of 
an interpreted language.  go nuts.  i sure do.  there are user-code 
insertion points all over my app.  ;)


Using eval in this way will probably be noticeably slower, FWIW. I 

would recommend exploiting object properties rather than John's 

example code, though sure, eval is useful in many contexts (see 

dynexpr.js example) when you need true dynamism.

Using eval in this way will probably be noticeably slower, FWIW. I  
would recommend exploiting object properties rather than John's  
example code, though sure, eval is useful in many contexts (see  
dynexpr.js example) when you need true dynamism.

Quote: pnyboer wrote on Sat, 10 June 2006 12:57

----------------------------------------------------

> These are for manipulation of an existing array, correct?

No, the code will create the array for you if it doesn't already exist, for both the add and clear functions.

Also does some checking (for presence of the the array.slice function) to ensure that you're not overwriting existing variables that aren't arrays - this is pretty much essential when using eval() to process input. You could just make a function that eval()s any symbol you poke at it and send it line after line of js from the outside world, but that could definitely be considered a little ... unwise.

As Joshua notes, eval() is not fast - I'd be wary of using this for anything realtime, I tend to use eval() for dynamic patch/variable setup, processing js-based preference files, etc.

Quote: pnyboer wrote on Sat, 10 June 2006 12:57
----------------------------------------------------
> These are for manipulation of an existing array, correct?

No, the code will create the array for you if it doesn't already exist, for both the add and clear functions. 

As Joshua notes, eval() is not fast - I'd be wary of using this for anything realtime, I tend to use eval() for dynamic patch/variable setup, processing js-based preference files, etc.


create Array dynamically?