As can be used:
•Meaning “because”
👉 As it was raining, we stayed at home. (como estaba lloviendo…)
•Meaning “while” or “at the same time”
👉 As I was walking down the street, I saw Julie (a la que caminaba…)
•To talk about the way one thing is similar to another thing. In this case we use the structure as + subject + verb
👉 John loves spicy food, as I do
👉 She’s as clever as her sister is
•To talk about similarity with expressions like “as much as” and “as adjective as”
👉 Lucy travels as much as me (tanto como yo)
👉 This house is as big as yours (tan grande como la tuya)
•To show someone’s (or something’s) role or position with the formula as + noun
👉 She works as a teacher (trabaja de…)
👉 Don’t use the knife as a screwdriver (no lo uses de…)
Like can be used:
•To give examples. It means the same as “for example” and is usually followed by nouns or pronouns
👉 Western European countries like France and Spain have high unemployment
•To talk about similarities (followed by a noun or a pronoun)
👉 Tokyo is a busy and exciting city, like London
Often, we can use both as and like to talk about similarity, indistinctively
👉 I love coffee, like Julie (like+noun)
👉 I love coffee, as Julie does. (as+subject+aux)