shrink keys

function shrink() {
        if (!(app.project.activeItem instanceof CompItem)) return;

        var currentComposition = app.project.activeItem;

        if (!currentComposition.selectedProperties.length) return;

        var properties = currentComposition.selectedProperties;

        app.beginUndoGroup("Shrink Keys");

        for (var index = 0; index < properties.length; index++) {
            var keyframeData = [];
            var property = properties[index];

            if (!property.numKeys) continue;

            for (var keyIndex = 1; keyIndex <= property.numKeys; keyIndex++) {
                keyframeData.push(property.keyValue(keyIndex));
            }

            for (var keyIndex = 0; keyIndex < keyframeData.length; keyIndex++) {
                var keyframeValue = keyframeData[keyIndex];
                var time = keyIndex * currentComposition.frameDuration;
                property.setValueAtTime(time, keyframeValue);
            }

            for (var keyIndex = property.numKeys; keyIndex > keyframeData.length; keyIndex--) {
                property.removeKey(keyIndex);
            }
        }
        app.endUndoGroup();
    }