Develop Reference

Don't understand why my for loop code isn't working

I was playing with the break and continue keyword but I notice in chrome console this code doesn't work
for (let i = 0; i > 5; i++) {
console.log(i);
} //this will print all number from 1 to 5 but console showing undefined
However I tried changing i = 5 or i === 5 still it doesn't work
But when I changed it to i < 5 then it yields correct result.
Why is that?

your condition is i > 5. At the beginning i = 0 so it will not run ever.
put i < 5

Please check following diagram
Condition getting false on the first time so code block won't execute

i<5 indicates that the for loop will run as long as i is less than 5. i>5 indicates that 0 is less than 5 (let i = 0). So the correct program should be -
for (let i = 0; i <= 5; i++) {
console.log(i);
}

jquery $.each vs for loop (with async content)

What is the main difference between:
var test=[5,6,7,8,9];
$.each(test, function (i, num) {
setTimeout(function(){console.log('i: '+i+' '+num)},500);
});
for (var j = 0; j < test.length; j++) {
setTimeout(function(){console.log('j: '+j+' '+test[j])},500);
}
First loop outputs:
i: 0 5
i: 1 6
i: 2 7
i: 3 8
i: 4 9
Second loop outputs:
5 times 'j: 5 undefined'
I understand why the second loop does this, but not why $.each works 'as expected'
Thanks!

In the first snippet's behind the scene, for every iteration the call back that you have supplied will be called. That means, internally it will create a scope per iteration. That eventually becomes a cloure.
But in the second snippet. The initial scope will be used while the timeout's call back got triggered. So it is displaying that output. And you can make it work by using the following code,
for (var j = 0;j<test.length-1;j++) {
var scope = function(i) {
setTimeout(function(){console.log('j: '+i+' '+test[i])},500);
};
scope(j);
}

Imacros - Looping multiple macros specific number of times using Javascript

I play multiple Macros one after another, multiple times using a simply loop in javascript .js file as below
var i;
for (i = 1; i <= 10; i++)
{
iimSet("loop", i);
iimPlay("1.iim");
iimPlay("2.iim");
iimPlay("3.iim");
}
but within the loop, i want each macro to be played specific number of times.
Say 1.iim 4 times, 2.iim 4 times and 3.iim full 10 times
How can i do that?
I tried adding "if" statement within the "for" loop for each macro
Var i1;
if(i1 <=4)
{iimPlay("1.iim");
i1++;}
But that didn't work :(
TIA

I would go with the "If" this way:
var i;
for (i = 1; i <= 10; i++) {
iimSet("loop", i); //this will be run 10 times
if(i<=4) {
iimPlay("1.iim");//this will be run during the 4 first loops
}
if(i>4 && i<=8) {
iimPlay("2.iim");//this will be run during the 4 next loops
}
iimPlay("3.iim"); //this will also be run 10 times
}

Nested Javascript for loops with break and label statements

I'm kinda new to Javascript and currently going over the book Professional Javascript for Web Developers and I came across this code which uses a break statement to exit the current loop and jump to a label named outermost.
Now I understand what break and labels do but I can't wrap my head around why the value ends up being 55 at the end?
Ok so the for loop with var i will loop 4 times then at 5 it breaks out to label:outermost and same with j so the first iteration i = 4 and j = 4 and num = 2. I guess this part confuses me.. at what point does the code stop. My first instinct if I were to code this from scratch is to have an outside variable and set the condition on that. But with the below code I don't get where the control structure lies and the final value. Appreciate any help or to be pointed in the right direction, thanks.
var num = 0;
outermost:
for (var i=0; i < 10; i++) {
for (var j=0; j < 10; j++) {
if (i == 5 && j == 5) {
break outermost;
}
num++;
}
}
alert(num);

This nested loop is emulating an odometer. i is the 10's digit, j is the 1's digit. Every time the 1's digit changes, num is incremented; at the start of each iteration, num contains the odometer's value.
The loop stops when both i and j are 5. At that point, the odometer would read 55, and that's what is in num.

When i was 0 to 4, the innermost loop is executed 50 times. When i = 5, the innermost loop is executed just 5 times until it reached i==5 && j==5 and jumped out. So it's total of 55 times.

how restricted is recursion in javascript?

I guess its to stop browsers getting nailed all the time by duff code but this:
function print(item) {
document.getElementById('output').innerHTML =
document.getElementById('output').innerHTML
+ item + '<br />';
}
function recur(myInt) {
print(myInt);
if (int < 10) {
for (i = 0; i <= 1; i++) {
recur(myInt+1);
}
}
}
produces:
0
1
2
3
4
5
6
7
8
9
10
10
and not the big old mess I get when I do:
function recur(myInt) {
print(myInt);
if (int < 10) {
for (i = 0; i <= 1; i++) {
var x = myInt + 1;
setTimeout("recur("+x+")");
}
}
}
Am I missing something or is this how you do recursion in JS? I am interested in navigating trees using recursion where you need to call the method for each of the children.

You are using a global variable as loop counter, that's why it only loops completely for the innermost call. When you return from that call, the counter is already beyond the loop end for all the other loops.
If you make a local variable:
function recur(int) {
print(int);
if (int < 10) {
for (var i = 0; i <= 1; i++) {
recur(int + 1);
}
}
}
The output is the same number of items as when using a timeout. When you use the timeout, the global variable doesn't cause the same problem, because the recursive calls are queued up and executed later, when you have exited out of the loop.

I know what your doing wrong. Recursion in functions maintains a certain scope, so your iterator (i) is actually increasing in each scope every time the loop runs once.
function recur(int) {
print(int);
if (int < 10) {
for (var i = 0; i <= 1; i++) {
recur(int+1);
}
}
}
Note it is now 'var i = 0' this will stop your iterators from over-writing eachother. When you were setting a timeout, it was allowing the first loop to finish running before it ran the rest, it would also be running off the window object, which may remove the closure of the last iterator.

Recursion is very little restricted in JavaScript. Unless your trees are very deep, it should be fine. Most trees, even with millions of elements, are fairly wide, so you get at most log(n) recursive calls on the stack, which isn't noramally a problem. setTimeout is certainly not needed. As in your first example, you're right that sometimes you need a guard clause to guarantee that the recursion bottoms out.