Query in mongodb within two joined collections

If I have a collection of employees and a collection of their salaries. How can i find the employee with highest salary and lowest?

Employee:{
{id:123, 
name:abc},
{id:456, 
name:efg}
}

Salary:{
{id:123, 
amou开发者_C百科nt:100},
{id:456, 
amount:200}
}

Currently I am using node js and mongooses in my project.