javascript - looping a triangle with a while loop -

i reading eloquent javascript book. there task build triangle this:

# ## ### #### ##### ###### ####### 

with loop.

i did loop.

for (var result = "#"; result.length <=7; result = result + "#") console.log(result); 

but reason can't while loop.

var result = "#" while(result.length <=7 ){ console.log(result); result = result + "#"; } vm920:3 # vm920:3 ## vm920:3 ### vm920:3 #### vm920:3 ##### vm920:3 ###### vm920:3 ####### "########" 

for reason getting line @ bottom 8 # symbols wrapped in quotes. why happening?

it's result of final expression in code. type in "5+5" in js console , you'll result. if put "5+5" @ end of script, same thing. that's what's happening here:

var result = "#" while(result.length <=7 ){     console.log(result);     result = result + "#";  // <-- last statement executed, returned } 

in contrast, last statement below logging statement, has no return value. result of script undefined.

for (var result = "#"; result.length <=7; result = result + "#")     console.log(result); 

you can see more if try this:

for (var i=0; < 5; i++) {      console.log(i);       } 

here, last expression i. code prints each number 0-4 inclusive, prints 4 second time because final expression.

0 1 2 3 4  <-- final console.log() call 4  <-- final expression