This method is like _.assign except that it accepts customizer which
is invoked to produce the assigned values. If customizer returns undefined
assignment is handled by the method instead. The customizer is invoked
with five arguments: (objValue, srcValue, key, object, source).
This method is like
_.assignexcept that it acceptscustomizerwhich is invoked to produce the assigned values. Ifcustomizerreturnsundefinedassignment is handled by the method instead. Thecustomizeris invoked with five arguments: (objValue, srcValue, key, object, source).Note: This method mutates
object.