英语中的ifOne night,the gaoler decided to play a joke on his col

英语中的if
One night,the gaoler decided to play a joke on his colleague to find out if,after so many performances,he had managed to learn the contents of the letter by heart.中插入语IF为什么在前面 可以放在后面吗
这是译文：
一天晚上，狱卒决定与他的同事开一个小玩笑，看看他反复演出这么多场之后，是否已将信的 内容记熟了。