Remove all channel masks except 4 default channels

Sorry, forgot to mention that Script also removes Paths except a possible Clipping Path and Vector Masks. 

// Remove all alphas, not spot
var myChannel = app.activeDocument.channels;
for (n = myChannel.length - 1; n >= 0; n--) {
    var value = myChannel[n];
    aC = myChannel[n];
    if (aC.kind == "ChannelType.MASKEDAREA") {
        aC.remove();
    }
}

// Remove all spot channels, not alphas
var myChannel = app.activeDocument.channels;
for (n = myChannel.length - 1; n >= 0; n--) {
    var value = myChannel[n];
    aC = myChannel[n];
    if (aC.kind == "ChannelType.SPOTCOLOR") {
        aC.remove();
    }
}

// Remove all channels, both alpha and spot
var myChannel = app.activeDocument.channels;
for (n = myChannel.length - 1; n >= 0; n--) {
    var value = myChannel[n];
    aC = myChannel[n];
    if (aC.kind != ChannelType.COMPONENT) {
        aC.remove();
    }
}

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html

An old script from @xbytor 

app.displayDialogs = DialogModes.NO;
// remove all paths,
if (app.documents.length == 0) { 
} 
else { 

var InitialPathCount = activeDocument.pathItems.length; 
var PathCount = activeDocument.pathItems.length; 
var PathList = new Array( ); 

for (var i = 0; i < PathCount; i++) { 
 	PathList[i] = activeDocument.pathItems[i].name 
} 

for (var i = 0; i < PathCount; i++) { 
if (activeDocument.pathItems[PathList[i]].kind != PathKind.CLIPPINGPATH) { 
if (activeDocument.pathItems[PathList[i]].kind != PathKind.VECTORMASK) { 
activeDocument.pathItems[PathList[i]].remove() 
} 
} 
} 
};
activeDocument.guides.removeAll();
// remove every but the composite channels,
if (documents.length > 0)
{
	docRef = activeDocument;

	for (var i = docRef.channels.length-1 ; i >=0 ; i--) {
	if (docRef.channels[i].kind != ChannelType.COMPONENT && docRef.channels[i].kind != ChannelType.SPOTCOLOR)	{
//		$.writeln(docRef.channels[i].kind);	
		docRef.channels[i].remove(); } 
	}
};
function deselectLayers() { 
    var desc01 = new ActionDescriptor(); 
        var ref01 = new ActionReference(); 
        ref01.putEnumerated( charIDToTypeID('Lyr '), charIDToTypeID('Ordn'), charIDToTypeID('Trgt') ); 
    desc01.putReference( charIDToTypeID('null'), ref01 ); 
    executeAction( stringIDToTypeID('selectNoLayers'), desc01, DialogModes.NO ); 
};