The JavaScript code attempts to log the type of an undefined variable undef to the console, but throws a ReferenceError instead. When trying to log the result of the expression undef || {"too much": false}, it returns the object literal {"too much": false} to the console due to the undefined value of undef.

Cell 5

console.log(typeof undef)
console.log(undef || {"too much": false})

// Define a constant for the undefined variable
const UNDEF = undefined;

/**
 * Returns the type of the undefined variable.
 * 
 * @returns {string} Type of the UNDEF.
 */
function getTypeOfUndef() {
  return typeof UNDEF;
}

/**
 * Returns a fallback object if UNDEF is truthy.
 * 
 * @returns {Object} Fallback object.
 */
function getFallbackObject() {
  return UNDEF || { "too much": false };
}

// Use the functions to print the results
console.log(getTypeOfUndef());
console.log(getFallbackObject());

Code Breakdown

Line 1: console.log(typeof undef)

• undef is an undefined variable.
• typeof is a unary operator that returns the type of its operand.
• The code logs the type of the undef variable to the console.
• Since undef is not declared or initialized, this line will throw a ReferenceError.

Line 2: console.log(undef || {"too much": false})

• undef is an undefined variable.
• The || operator is a logical OR operator that returns the first "truthy" value it encounters.
• When used with variables, it returns the variable if it is not empty (i.e., not undefined, null, or zero), and the value on the right side if the variable is falsy.
• In this case, since undef is undefined, the expression undef || {"too much": false} will evaluate to the object literal {"too much": false}, which will be logged to the console.