ee.ImageCollection.combine

Makes a new collection that is a copy of the images in primary, adding all the bands from the image in secondary with a matching ID. If there's no matching image, the primary image is just copied. This is equivalent to a join on ID with merging of the bands of the result.

Note that this algorithm assumes that for a matching pair of inputs, both have the same footprint and metadata.

UsageReturns
ImageCollection.combine(secondary, overwrite)ImageCollection
ArgumentTypeDetails
this: primaryImageCollectionThe primary collection to join.
secondaryImageCollectionThe secondary collection to join.
overwriteBoolean, default: falseIf true, bands with the same name will get overwritten. If false, bands with the same name will be renamed.