(JS) make for-loop function go from last to first

Question

This code is now making 1 to 4. How can it make 4 to 1 (last to first)?

var nb = 4;
var first = ' active';
if (nb > 1) {
    for (var i = 1; i <= nb; i++) {
        page  = page+'<span class="to-step-nb'+first+'">'+0+String(i)+'</span>';
        first = '';
    }
}

There are a thousand ways to loop backwards, and I'm sure you could have googled it a lot faster than the time it took to write the question, but here you go, my favorite backwards loop: for(var i=len;i-->1;) { .. } — Jite
– Jite, Commented Sep 4, 2015 at 11:23
possible duplicate of What is the most efficient way to reverse an array in Javascript? — romuleald
– romuleald, Commented Sep 4, 2015 at 11:29

Tushar · Accepted Answer · 2015-09-04 11:26:05Z

8

nb should be number not string
You're missing } at the end
Use the condition
```
for (var i = nb; i > 0; i--)
```
to reverse the loop.
String(i) is not required
first is set to empty string, after first iteration, so now, you'll have last item active
if (nb > 1), is not required, as if the condition fails, for will not execute
You can use Shorthand for a = a + .. as a += ..

Code:

var nb = 4;
var first = ' active';

for (var i = nb; i > 0; i--) {
    page += '<span class="to-step-nb' + first + '">' + 0 + i + '</span>';
    first = '';
}

edited Sep 4, 2015 at 11:26

answered Sep 4, 2015 at 11:20

Tushar

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4 Comments

mamady Over a year ago

Question.. Now it thinks 4 is first and adds +first+ to the class, How can I make 1 first so 1 will get +first+ class?

Tushar Over a year ago

Use if statement in loop to check and add

mamady Over a year ago

Would you please show me like I have no JS knowledge (because I don't!)

mamady Over a year ago

I tried for (var i = nb; i > 0; i--) { if (i = 1) { first = ''; } } but it doesn't work

Vittorio · Accepted Answer · 2015-09-04 11:21:36Z

0

for (var i = nb; i >= 1; i--) {
  // do something
}

answered Sep 4, 2015 at 11:21

Vittorio

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