How exactly does a for/in loop work?


I've created the following code and it has been deemed correct by the lesson, although I am still confused by the 'for/in' loop.

How am I able to put in anything I want for the "for(var sas in friends)" portion of the code. Am I declaring a new variable IN the object called "sas"? In this case I picked "sas" for the variable but it looks like I can make it anything as long as I make it consistent.

Just wanting to find out what exactly it's doing there....

var friends = {};
    friends.bill = {
        firstName: "Bill",
        lastName: "Sanders",
        number: "(512)-230-1716",
        address: ['1111 Mushy Drive', 'New York', 'NY', '22222']
    friends.steve = {
        firstName: "Steve",
        lastName: "Williams",
        number: "(832)-540-1111",
        address: ['2321 Wannabe Lane', 'Houston', 'TX', '71111']

var list = function(friends){
    for(var qwk in friends){

var search = function(name){
    for(var sas in friends){
        if(friends[sas].firstName === name){
            return friends[sas]




T h e - B a s i c s

An object has one or more properties seperated by a comma-,
Each property consists of a property-key and it's associated VALUE

var nyc = {
       fullName: "New York City",
       mayor: "Bill de Blasio",
       population: 8000000,
       boroughs: 5
nyc -object- S p e c i f i e d

The nyc object has 4 properties seperated by a comma-,
- a fullName property with property-key fullName and it's associated string value of "New York City"
- a mayor property with property-key mayor and it's associated string value of "Bill de Blasio"
- a population property with property-key population and it's associated number value 8000000
- a boroughs property with property-key boroughs and it's associated number value 5

for - in - loop - e x p l a i n e d

With the for-in-loop you have a Method
which will iterate over all properties of a given object.
At each iteration it will assign the property-key as a string
to a variable name of your choice.
Thus for (var x in nyc)
will lead to 4 iteration's
iteration-1 var x = "fullName";
iteration-2 var x = "mayor";
iteration-3 var x = "population";
iteration-4 var x = "boroughs";
As they want you to display the property-key and NOT it's associated VALUE
you would use
console.log( x );

If they wanted you to display the associated VALUE of the propery-key you would use
console.log( nyc[x] );


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