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Comments

If needed, you can add comments to a program. Comments are used to explain programs. They help us humans to understand programs. Computers ignore comments.

In JavaScript there are two ways to write comments: Line comments are introduced with // and are valid until the end of the line. Block comments start with /* and end with */. Any text in between is a comment.
// That's a line comment.

// This line comment
// covers 2 lines.

/* That's a block comment. */

/* This line comment
covers 2 lines. */

/**
 * This is also a block comment.
 * The additional stars between
 * the beginning and the end of the
 * block comment are only for decoration.
 */
Block comments are often used to explain functions. Line comments explain the code flow.
/**
 * Checks whether a string contains
 * any characters other than spaces.
 */
var isEmpty = function(string) {
  // The method trim() removes spaces at 
  // the beginning and the end of a string.
  var trimmedString = string.trim();
  return trimmedString.length === 0;
};
Comments can't be checked with the tests used here. It follows a task where you have to apply much of what you have learned so far.

Exercise

Write a function median that takes an array of ascending numbers and returns the median of that numbers. median([1, 2, 10]) should return 2 and median([1, 2, 10, 100]) should return 6.
The median of a sorted series of numbers is the value in the middle. If the number of values is even, the median is the mean of the two middle numbers.