How do you spell it?

To tell unequivocally, as it is written on former,it is impossible. It is necessary to know the whole sentence in which this word stands, and its meaning. "As before" can be an adjective with a preposition and an adverb. Let's consider both variants.

1. Example. "People were still running around the street bustlingly, cars were rushing". As before, this is an adverb, answering the question "How did they run?" Such adverbs have suffixes-to-you, -em, -ski, -ski: still, in a good way, in good, in a bad way. Such adverbs are written only through a hyphen. Therefore, when "as before" is in the sentence an adverb, then we write this: as before.
2. If this is an adjective, then the word is writtenseparately, because "on" here is an excuse, and "former" is an adjective. For example: "We went along the old way, which was supposed to bring us to the village." The path is a noun, the adjective "former" refers to it, they form the phrase "along the old way". The word answers the question: "On which path?" - as before. When "as before" is in the sentence an adjective with a preposition, we write them separately.

To understand how to write this sentence correctly in a sentence, you need to look at the context and ask the question for the word. Well and as it is written on former in each of these cases, you already know.