Jon Rumsey

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Power Hour Talk: All About Loops

Presenter: Kassie Bradshaw, Python Alum

"repl"

KB used replit.com as the presentation

Trivia

JavaScript has 7 types of loops.

Looping Code in General

Just says "execute code within brackets".
Usually includes some sort of condition under which the loop exits.

For Loop

for (Where is the loop going to start?, Loop runs while this condition is true, How much will variable be incremented while loop is running? ) { code }

Foreach Loop

Is an Array prototype method.
let myArray = ["one", "two", "three"];
arrayName.forEach(function(item, index){ do... });
Why use this instead of a for loop?

• If you have the option of using a prototype method, use it!
• PMs are better optimized for working with iterables.
• Will only get back items that are actually defined; a benefit of a prototype method.

Can use the "arrow function" to operate on each iterable.
myArray.forEach( item => console.log(item));

While Loop

Map

Loops over an array, creating a new array and modify it with results from operations against the source array.
Usage: let newArray = myArray.map(item => { let newItem = 'Value: ${item}'; console.log(newItem); return newItem;});

For...In and For...Of Loops

Is meant to iterate over the properties of an object.
Can operate on arrays as well as objects, however:

• forin when operated on arrays will return the indices of the array items (think for keys in array).
  -- It can get the values when using the key as the argument to the object indexer.
• forof is used similarly to a For() loop.

ForOf loop is the newest loop released.
ForOf loop can iterate over any iterable object.
ForOf loop is a simplified version of the For() loop, in that code is shorter but just as effective.

let myObject = { school: "codefellows", activity: "pph", time: "noonish"};
let myArray = ["hi", "howedy", "how are ya?"];

Code expaining how to use For...In to return values by using the keys:
myArray.forIn(i => Console.Log( myArray[i] )); (this needs to be verified).

Breaking Out Of A Loop

There are a few ways?

1. Use conditional with a break statement e.g. if(j=2){break;}.
2. Use an additional conditional that increments the tracking variable for ex: if ( condition ) { indexer = top indexer value};.