Accumulator Questions - In class follow up

Struggling with the for-in loop and the differences between the terminology of -variable, property, key, and value, 
in relation to Objects and this type of loop.  It really wasnt covered very well in Objects 
or accumulator patterns Lectures for my novice brain.   




#1   Write a function named invert that takes an object and returns an object
    where the keys and values have been inverted

    Example:

    If you pass {id: 1, name: "Joe"} it should return {1: "id", Joe: "name"}
    */
    
    
    
    
#2   Write a function named index that takes an array of objects, and a
    property name, and returns an object where the keys are the specified property

    Example:

    If you pass [{id: 1, name: "Joe"}, {id: 2, name: "Sue"}] it should
    return {1: {id: 1, name: "Joe"}, 2: {id: 2, name: "Sue"}}

    */
    
    
    
 #3 Write a function named addSignature that takes an object and a name, and returns an object where
    - the keys are suffixed with "-signed"
    - the values are suffixed with " - <name>"
    
    Example:
    If you pass {"contract": "foo"}, "Fred" it should return {"contract-signed": "foo - Fred"}
    */
    
    
    
  #4 Write a function named pairs that takes an object and returns an array of s
    trings of key/value pairs

    Example:

    If you pass {name: "Will", age: 24} it should return ["name - will", "age - 24"]
     */
        
        
        
        
   #5  Write a function named containsValue that takes an object and a
       value and returns true if the object contains the value

      Example:

      If you pass {1999: 4036, 2000: 7654} and 4036, it should return true
       */