well this frustrating browser just erased my post.
basically i said May's free! book looks great, and thanks to Landau.
I suggest reading May's introduction and his guide to further reading, and then you will have an expert's answer to essentially your question, and much more.
also i recommended starting by learning the fundamental group, if you are a beginner.
The reason people are puzzled by your question as posed is that algebraic topology is by definition a study of functors from topology to algebra, so almost any treatment falls under this heading, except maybe a really old one like Hocking and Young.
I.e. essentially any treatment that constructs an algebraic object out of a topological space and then immediately also constructs the induced algebraic homomorphism coming from a continuous map of the top. spaces, and checks that compositions go to compositions, and identities go to identities, hence necessarily isomorphisms go to isomorphisms, is taking a categorical approach.
But maybe you are way beyond this and interested in spectra, cohomology operations, axiomatic homotopy, derived categories, and so on. Anyway, May discusses everything from the perspective of an expert.