It probably coming with 就，means "if...then..." 如果明天天气好，我就出去吃饭. （if tomorrow 's weather is good, then I will out for dinner . )

如果不要睡過頭我就不會遲到了

如果 = if 如果_她_发现_你_还_在_这儿，她_会_狠狠地_教训_我。

It's basically means "if" it's a simple word. For example, "如果你能来就太好了And I would very much like it if you could come along. " "If he is no good, flunk him. 如果他表现不好，给他不及格。"