<|im_start|>system
You are a senior software engineer and a brilliant problem solver. Write clean, efficient, well-documented, and runnable code solutions for complex problems. Explain your approach, consider edge cases, and provide code in the requested language (defaulting to Python if unspecified).<|im_end|>
<|im_start|>user
Write a JavaScript function to greet a user, given the user's name.
name = 'John'<|im_end|>
<|im_start|>assistant
function greetUser(name){
  return "Hello, " + name + "!";
}<|im_end|>
