Как я могу решить эту проблему в javascript ?

---

Create the javascript code for the next problems:

    Compute the sum of odd numbers from 1 to n.
    Send to output all numbers from 1 to n (read n from input) dividing with 3 or 5.
    Find the minimum number in an array. 
    Given an array of strings, output the total number (count) of characters in the list. Example: a = ["ana", "are", "mere"] => count = 10; for a = [] (empty array, with no elements), count = 0.

Extra-mile: 

    (Extra-mile) Given a list of elements, output the number of elements.
    (Extra-mile) Given a mathematical expression as a string, evaluate the expression and output the result.

Что я уже пробовал:

var n=parseInt (prompt ("n=0"));
		if (n==0)
		{
		   alert ("Sum=0");
		}  
		else                                                                                              
		{  
		var s=0;
		var i=n;
			do
            {
				s=s+i;
				i=i-1;
	        }while (i!=0)  
			
			alert("Sum=" +s);

---