Using "look" without preposition

Question

I came across with this sentence where "look" was used without preposition afterward. Isn't both ways a noun phrase ? In the other sentences "look" was used before a preposition so what is the different between them ?

1- Be careful to look both ways when you cross the road.

The other examples :

2- They looked at the picture and laughed.

3- Look at all these toys on the floor.

Answer 1

In "Look both ways," both ways is more an adverbial phrase, adverting to a position.

It's parallel to using up after look. If you say "Look up," up is an adverb.

up adv
1 a. In or to a higher position: looking up.
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