Shouldn't the variable pass through the condition in a "for" loop?

Curriculum Help JavaScript
#1

Tell us what’s happening:

Your code so far


// Setup
var myArray = [];

// Only change code below this line
for(var i = 1; i < 10; i += 2) {
myArray.push(i)
}

console.log(myArray)

The lesson showed an example of a “for” loop:

var ourArray = [];
for (var i = 0; i < 10; i += 2) {
  ourArray.push(i);
}

But when I replicate the exact same code it and console.log it, it shows [ 0, 2, 4, 6, 8 ].
My question is: shouldn’t 8 pass through the condition then become 10 since 8 is less than 10?

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Challenge: Iterate Odd Numbers With a For Loop

Link to the challenge:

#2

I’m confused by your question. 8 is less than 10, so it gets pushed onto ourArray.

#3

Loop execution has 3 stages

  1. Check exit condition
  2. Execute loop body
  3. Increment loop iterator

When i == 8, the exit condition has not been met, so the loop body executes and then the iterator increments to i == 10, which causes the exit condition to trigger.

#4

Yes, but shouldn’t 8 get passed to the final-expression to += 2 to become 10

#5

It does. It gets added to the array, then increments by 2, then the loop exits.

#6

so after the condition has been met it checks again to see if it triggers the exit condition?

#7

so it checks again if it matches the condition, right?

#8

It checks at the start of every iteration. After i becomes 10, that check is false, so the loop exits and 10 is not added to the array.

#9

The three steps are always in that order.

  1. Check exit condition
  2. Execute loop body
  3. Increment loop iterator

For this function

  1. loop initializes, i == 0
  2. iteration 0
    a) check exit condition, i < 10 :heavy_check_mark:
    b) execute loop body, push 0 onto the array
    c) increment loop iterator, i == 2
  3. iteration 1
    a) check exit condition, i < 10 :heavy_check_mark:
    b) execute loop body, push 2 onto the array
    c) increment loop iterator, i == 4
  4. iteration 2
    a) check exit condition, i < 10 :heavy_check_mark:
    b) execute loop body, push 6 onto the array
    c) increment loop iterator, i == 8
  5. iteration 3
    a) check exit condition, i < 10 :heavy_check_mark:
    b) execute loop body, push 8 onto the array
    c) increment loop iterator, i == 10
  6. iteration 4
    a) check exit condition, i < 10 :heavy_multiplication_x:
  7. execution halts and loop is finished
1 Like
#10

oooohhh i get it now xD thanks mate!!

1 Like
#11

I get it now, Thank you so much!!