Javascript TypeError: Cannot read property '1' of undefined

Question

var toplamgun = 0; var toplampazar = 0; for (var yıl = 1900; ++yıl < 2001;){ for(var ay= 0; ++ay<13;){ if (ay == 2){ } else{ var eklenecekgun = AydakiGunler[ay] // error is here toplamgun += eklenecekgun yenigunindex = toplamgun % 7; if(yenigunindex == 6){ toplampazar += 1; } } } } console.log(toplampazar); var AydakiGunler = [0,31,0,31,30,31,30,31,31,30,31,30,31];

cant get an item from an array by index

here is the error TypeError: Cannot read property '1' of undefined

im trying to https://projecteuler.net/problem=19

well, AydakiGunler isn't defined until after the code is run - var declarations are hoisted, but not the value — Jaromanda X
– Jaromanda X, Commented Apr 13, 2020 at 10:32

Inobulles · Accepted Answer · 2020-04-13 10:34:25Z

You need to define AydakiGunler before trying to access it. Your code would then look like this:

var AydakiGunler = [0,31,0,31,30,31,30,31,31,30,31,30,31]; var toplamgun = 0; var toplampazar = 0; for (var yıl = 1900; ++yıl < 2001;){ for(var ay= 0; ++ay<13;){ if (ay == 2){ } else{ var eklenecekgun = AydakiGunler[ay] // error is here toplamgun += eklenecekgun yenigunindex = toplamgun % 7; if(yenigunindex == 6){ toplampazar += 1; } } } } console.log(toplampazar);

I'm afraid I don't speak Turkish, so I can't help you any further in what you're trying to do, but either way I wish you the best of luck.

Mahdi Ghajary · Accepted Answer · 2020-04-13 10:33:19Z

Define AydakiGunler before your for loop.

var variables are hoisted and declared at the top your file but they're undefined before its initialization.

 var toplamgun = 0; var toplampazar = 0; var AydakiGunler = [0,31,0,31,30,31,30,31,31,30,31,30,31]; for (var yıl = 1900; ++yıl < 2001;){ for(var ay= 0; ++ay<13;){ if (ay == 2){ } else{ var eklenecekgun = AydakiGunler[ay] // error is here toplamgun += eklenecekgun yenigunindex = toplamgun % 7; if(yenigunindex == 6){ toplampazar += 1; } } } } console.log(toplampazar);

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