Iterate with JavaScript For Loops
The most common type of JavaScript loop is called a for loop
because it runs for
a specific number of times.
var ourArray = [];
for(var i = 0; i < 5; i++) {
ourArray.push(i);
}
ourArray will now contain [0,1,2,3,4]
More about for loops
for(var i = 0; i < 5; i++) { // There are 3 parts here
There are three parts to for loop. They are separated by semicolons.
The initialization:
var i = 0;
- This code runs only once at the start of the loop. It's usually used to declare the counter variable (withvar
) and initialize the counter (in this case it is set to 0).The condition:
i < 5;
- The loop will run as long as this istrue
. That means that as soon asi
is equal to 5, the loop will stop looping. Note that the inside of the loop will never seei
as 5 because it will stop before then. If this condition is initiallyfalse
, the loop will never execute.The increment:
i++
- This code is run at the end of each loop. It's usually a simple increment (++
operator), but can really be any mathematical transformation. It is used to move the counter (i
) forward (or backwards, or whatever.