Mongoose validate unique field (insensitive)

Making a validation function for Mongoose (Node.js – MongoDB ODM) that checks upon validation field.

function uniqueFieldInsensitive ( modelName, field ){
	return function(val, cb){
		if( val && val.length ){ // if string not empty/null
			var query = mongoose.models[modelName]
				.where( field, new RegExp('^'+val+'$', 'i') ) // lookup the collection for somthing that looks like this field 
			if( !this.isNew ){ // if update, make sure we are not colliding with itself
				query = query.where('_id').ne(this._id)
				// false when validation fails
				cb( n < 1 )
		} else { // raise error of unique if empty // may be confusing, but is rightful
			cb( false )

Then call it to a field (aka path):

UserSchema.path('nick').validate( uniqueFieldInsensitive('User', 'nick' ), 'unique' )

Recommend you organize all validations in a file for itself, or even a folder if grows too big.

If you have a unique index set for the path you may just save it and check for the error raised; the thing is the format of the error.