Indesign Scripting: Loop through Layers

I am trying to make a script that will:

Loop through all layers of a document.

Add the unlocked layers to array

Loop through this array and paste in place on each layer.

I am not sure how to loop through all layers.

Here is my script (I have used ??? to represent where the loop through all layers part would go):

// JavaScript Document

//Set up an array to hold unlocked layers

var layercollection = [];

 

//Loop through Layers and unlocked layers to the layercollection array

for (i = 0; ? ? ? i++) {

          app.activeDocument.activeLayer = app.activeDocument.layers.itemByName( ? ? ? );

          if (app.documents[0].layers. ([i]).locked) == false;

          layercollection.push(layers.itemByName([i]))

}

 

// Loop through layercollection array and paste in place

for (i = 0; i < layercollection.length; i++) {

          app.activeDocument.activeLayer = app.activeDocument.layers.itemByName(tl[i]);

          app.pasteInPlace(); //Paste

}

 

Can someone help me complete my script.

Thanks!