Illustrate me why only str.length is not enough to reverse the string, why length-1 required ?

Question

var str="string";
var emstr="";
for (i=str.length-1;i>=0;i--)
emstr+=str[i];
console.log(emstr);

Answer 1

index value starts from 0.
so last index is 5 only . Should be str.length-1.

Answer 2

Not 4 it's 5.

str.length returns 6 , the length of string. and index values are 0,1,2,3,4,5 ; Check this code :

for( let i=0; i<str.length; i++)
console.log( "Index = "+i +" Value = "+str[i] ) ;

index 0 value 's' ;
...
...

so like :
0 -> 's'
1 -> 't'
2 -> 'r'
3 -> 'i'
4 -> 'n'
5 -> 'g'.

Answer 3

Then the 1st value of i is 4 and str[4] is n ....how it works?