This is an example and you can configure it as you like
if(documents.length){
var strtRulerUnits = app.preferences.rulerUnits;
var strtTypeUnits = app.preferences.typeUnits;
app.preferences.rulerUnits = Units.PIXELS;
app.preferences.typeUnits = TypeUnits.PIXELS;
var Width = app.activeDocument.width.value;
var Height = app.activeDocument.height.value;
var Min = Math.min(Width,Height);
var Max = Math.max(Width,Height);
if(Max >= 1200 && Max <= 1500){
var startRulerUnits = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PERCENT;
var doc = activeDocument;
var res= doc.resolution;
var LB = activeDocument.activeLayer.bounds;
var Width= LB[2].value - LB[0].value;
var onePrc = 100/Width;
var newSize = onePrc * 50; // percent
var newHSize = onePrc * 50; // percent
doc.activeLayer.resize( newSize , newHSize, AnchorPosition.MIDDLECENTER);
app.preferences.rulerUnits = startRulerUnits;
}
if(Max >= 1501 && Max <= 2100){
var startRulerUnits = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PERCENT;
var doc = activeDocument;
var res= doc.resolution;
var LB = activeDocument.activeLayer.bounds;
var Width= LB[2].value - LB[0].value;
var onePrc = 100/Width;
var newSize = onePrc * 40; // percent
var newHSize = onePrc * 40; // percent
doc.activeLayer.resize( newSize , newHSize, AnchorPosition.MIDDLECENTER);
app.preferences.rulerUnits = startRulerUnits;
}
app.preferences.rulerUnits = strtRulerUnits;
app.preferences.typeUnits = strtTypeUnits;
}