Change duration of layer in composition by the javascript in after effects

Question

Can anybody help me? I am trying to write a script for after effects CC using Extendscript. I want change duration of layer in composition by the javascript. I wrote this code here

app.project.item(1).layer(1).length = 12;

or

app.project.item(1).layer(1).duration = 12;

but it doesn't works. How can i do it? Thanks.

Answer 1

The thing is not that easy. Layers like Solids don't have a duration you can set. But you can set their inPoint and outPoint. Other layers like a comp need to be changed at their source. See the code below on how to do that.

function main(){
// do some checking if we have a comp and a layer selected
var curComp = app.project.activeItem;
  if (!curComp || !(curComp instanceof CompItem)) {
    // alert and end the script
    alert("please select a composition and at least a layer");
    return;
  }
var durationValue = 1; // the desired value in seconds
var selectedLayer = curComp.selectedLayers[0]; 

// if the layer has source layers it is a comp
// so we change its source duration
// else 
// we have layers like solids or lights. They have no source and no layers in them
// so we change their outPoint 

if (selectedLayer.source.numLayers != null){
    $.writeln('we have a comp');
    selectedLayer.source.duration = durationValue;
  } else {
    $.writeln('we have a layer');
    selectedLayer.outPoint =   selectedLayer.inPoint + durationValue;
  }
}
main();