prep-work/2- javascript/4-while-loops-and-for-each

While and For In Loops

In this challenge, we're going to write a while loop, a For In loop, and nest them.

While Loops

A while loop iterates until a condition is no longer true. For example:

while(greg == alive){
	live_year(1)
	age++
}

Seemingly, a while loop could be endless. In that case, we have to break it. Take the following example:

i = 0

while(true){
	i++
	print("I'm an endless loop")
	if(i >= 50){
		break;
	}
}

This will run exactly 50 times.

For In

A For In loop iterates through each index in the data structure. In an array, an index is an integer, that starts at 0. Take this example:

var array = ['john', 'bobby', 'homa', 'stevie', 'rob']

for(var i in array) {
	console.log(i) // prints 0, 1, 2, 3, 4
}

In an object however, the index is a string. Check this out:

var obj = {'john': 'student', 'bobby': 'programmer', 'homa': 'actress', 'stevie': 'gamer'}

for(var k in obj) {
	console.log(k) // prints 'john', 'bobby', 'homa', 'stevie'
}

Sandbox

Try this on your own in your node console or browser console. Declare some objects, iterate through them, print them out.

Also check out .forEach

Multiplication Tables

Using any loop / loops of your choosing, write code that prints the multiplication tables up to a number input by the user in a form.

Create the form that gets the user input yourself above the #printout div, and append the result to the printout div.

Bonus if you actually use a table.

Your return should look something like this:

// userinput = 7

0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
1 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
2 | 2 | 4 | 6 | 8 | 10| 12| 14|
3 | 3 | 6 | 9 | 12| 15| 18| 21|
4 | 4 | 8 | 12| 16| 20| 24| 28|
5 | 5 | 10| 15| 20| 25| 30| 35|
6 | 6 | 12| 18| 24| 30| 36| 42|
7 | 7 | 14| 21| 28| 35| 42| 49|