while (i --> 0) 是什么意思？

Question

I apologize if this a stupid question, but I cannot find the answer anywhere.

How does the following code work? (I realize that it loops over the elements of els )

var i = els.length;
while (i --> 0) {
    var el = els[i];
    // ...do stuff...
}

I have no idea what --> means. There is no documentation for it. Can someone enlighten me?

Answer 1

It should be read as

i-- > 0

So, what really happens is,

1. value of i will be checked if it greater than 0, if it is true then control will enter the while block, if it is false while block will be skipped.

2. Either way, the value of i will be decremented, immediately after the condition is checked.

Its always better to use for loop, when we run a loop with a counter, like this

for (var i = els.length - 1; i >= 0; i -= 1) {
    ...
}

Please read more about whether ++ , -- is okay or not.

Answer 2

It's just weird spacing, should be

while((i--) > 0)

it's just post-decrementing and checking the condition. There was this humorous answer at the C++ question, but I think it got deleted

while (x --\
            \
             \
              \
               > 0) //i goes down to zero!

Or something like that, anyway

So if you had something like

var i=3;
while(i-->0){
     console.log(i);
}

it would return

2
1
0

Answer 3

It's just weird spacing. It's same as

while (i--  >  0) {

Answer 4

The code should actually be:

while (i-- > 0) {

where the loop will run if the value after the variable i has been decremented is greater than zero.

Answer 5

while (i--> 0) 
{
    // ...do stuff
}

is same as

while (i>0) 
{
     i--;    
    // ...do stuff
}

IMHO we should write simple code rather than clever code because it's not understandable by everyone.