Posterize Keyframes.jsx

/**
 * @name Posterize Keyframes
 * @version 2.0
 * @author Kyle Martinez <www.kyle-martinez.com>
 *
 * @description Posterize all selected keyframes in a composition to be on 2s.
 *
 * > [!CAUTION]
 * > Currently this script does not respect easing, spatial interpolation, temporal interpolation,
 * roving keyframes, labels, or anything else. Results will always be linear keyframes.
 *
 * @license This script is provided "as is," without warranty of any kind, expressed or implied. In
 * no event shall the author be held liable for any damages arising in any way from the use of this
 * script.
 *
 * I'm just trying to help make life as an After Effects animator a little easier.
 */

(function posterizeKeyframes() {
    app.beginUndoGroup("Posterize Keyframes");
    var comp = app.project.activeItem;
    var frameDuration = comp.frameDuration;
    var properties = comp.selectedProperties;
    var numProperties = properties.length;
    for (var p = 0; p < numProperties; p++) {
        var property = properties[p];
        if (property.isTimeVarying == true) {
            for (var k = property.numKeys; k > 0; k--) {
                var oldTime = property.keyTime(k);
                var oldValue = property.keyValue(k);
                var oldFrame = Math.floor(oldTime / frameDuration);
                if (oldFrame % 2 != 0) {
                    property.removeKey(k);
                    var newFrame = oldFrame - 1;
                    var newTime = newFrame * frameDuration;
                    property.setValueAtTime(newTime, oldValue);
                }
            }
        }
    }
    app.endUndoGroup();
})();