How to make javascript variables global?

jplener · June 17, 2015

Hi,

I try to integrate javascript arrays into lectora. I created some js variables and functions, attached the script as HTML-Extension type Header Scripting (sorry I have the German version of Lectora - not sure if I translate correctly). Everything works fine, as long as I stay on one page. Jumping between pages destroys the object(s). How can I store a javascript array/object for the whole project / aka making it a global variable? Seems I initialize the variable in the wrong place, or do not properly integrate the js-functions.

Any hints are greatly appreciated! I have attached my test project (Lectora 12) ...

Joachim Plener

ssneg · June 17, 2015

Every Lectora's page is a separate HTML document. When navigating between pages, all scripts are loaded from scratch, all data is lost. Lectora uses Variable Manager to keep variables between pages. I never looked into how it works exactly, I just trust it to work. I assume it uses cookies (see attached screenshot).

So whenever I use JS arrays on a page, I serialize them and store in a Lectora variable before navigating away. Then when I need them on a different page, I read that variable and de-serialize the string into an array, using .split() and .join() respectively.

jplener · June 18, 2015

Thanks, Sergey for your fast reply! I had a feeling it could be that way and tried using a Lectora Variable for my array, by initializing it in Lectora and later redefining it as an array:

function initTriageArray(){
if (Var_triageArray.getValue() == 0){
Var_triageArray = new Array();
}
}

I could use it, but only on one page, probably because Lectora variables can`t hold objects and therefore are reinitialized on a new page. As my Javascript knowledge is pretty limited (coming from 5+ years with Adobe Director) I thought I did something wrong with my implementation of the javasccript functions.

But now I know what to do: Convert the array to a string before leaving and rebuild it upon entering a page.

Quite ugly, but if it works - nevermind...

Thanks again, Joachim

ssneg · June 18, 2015

Exactly, don't store arrays, store strings. The easiest way is to simply do this:

//before leaving
var arr = ["one","two","five"]
var str = arr.join(); // "one,two,five"
VarMyLectoraVariable.set(str);

//after loading new page
var str = VarMyLectoraVariable.getValue();
var arr = str.split(&#039;,&#039;); // ["one","two","five"]

Keep in mind that .join() will convert any numbers to strings, e.g.:

[1,2,3,4].join() --> "1,2,3,4"
"1,2,3,4".split(",") --> ["1", "2", "3", "4"]

Also, if any value in your array contains a comma, it will mess things up badly:

["Anna","Adams, John","Smith, Bob"].join() --> "Anna,Adams, John,Smith, Bob"
"Anna,Adams, John,Smith, Bob".split(",") --> ["Anna", "Adams", " John", "Smith", " Bob"] (oops!)

So if you want a robust way of serializing and de-serializing arrays for storing them as strings, use JSON.stringify() and JSON.parse() functions. It works like this:

var complex_arr = ["Anna","Adams, John","Smith, Bob", "1", 2, "4,3"]
var str = JSON.stringify(complex_arr) // &#039;["Anna","Adams, John","Smith, Bob","1",2,"4,3"]&#039;
var rebuild_array = JSON.parse(str) // "Anna", "Adams, John", "Smith, Bob", "1", 2, "4,3"]

Hope this helps.

jplener · June 18, 2015

Great! This does help indeed! I especially love that the JSON.stringifiy / parse functions can convert multidimensional arrays (with objects included) to a string and rebuild them. For example I have an array with many entries looking like that :

`[Before: Var_triageArray = new Array()]

function createNewObject(name, wert, score){
pos                                                           = Var_triageArray.length;
Var_triageArray[pos]                          = new Object();   // new "Array" 3 Entries
Var_triageArray[pos]["Name"]       = name;                 // String
Var_triageArray[pos]["Checked"]    = wert;                 // 0 or 1
Var_triageArray[pos]["Score"]     = score;                // 1 to 5
}`

These JSON functions had no problem to stringify and parse again that kind of an array with objects and mixed values (string and integer) included.

As your post reached me, I was in the middle of writing my own parser with split and join and new... Now I need two lines to save and two lines to restore!

Thanks again, Joachim

How to make javascript variables global?

Comments

Categories