Loop issue from Elegant javascript Chapter 2 Exercise 3 -

this question comes above source, in i'm asked make chess board. provided solution uses same method, except y < size , x < size. why doesn't way work?

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var size = 8; var chess = "";  (var y = 0; y == size; y++){     (var x = 0; x == size; x++){          if ((x + y) % 2 == 0)             chess += " ";         else             chess += "#";      }     chess += "\n";     }  console.log(chess); 

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you need understand how for loop works. read on @ https://developer.mozilla.org/en-us/docs/web/javascript/reference/statements/for.

the second clause condition checked each time through loop, including @ beginning. if false, loop exited. loop continues while true. in case, want keep looping until x or y has reached size of board (actually, size of board less 1, since starting @ 0). therefore, following is correct:

for (var y = 0; y < size; y++) {                 ^^^^^^^^ 

if did, , say

for (var y = 0; y == size; y++){                 ^^^^^^^^^ 

then loop never execute @ all. start off x of zero, check if equal size not (0 !== 8), , therefore exit loop without executing once.