arrays - eloquent javascript correlation tableFor explanation -


i taking first steps in programming , stuck problem eloquent, in particular weresquirrel problem. here goes :

function hasevent(event, entry) {  return entry.events.indexof(event) != -1; }  function tablefor(event, journal) {   var table = [0, 0, 0, 0];    (var = 0; < journal.length; i++) {      var entry = journal[i], index = 0;       if (hasevent(event, entry)) index += 1;       if (entry.squirrel) index += 2;       table[index] += 1;  }  return table; }  console.log(tablefor("pizza", journal)); // → [76, 9, 4, 1]

i understand first function hasevent, returns true if entry contains given event.

what can't grasp tablefor function. can't how function flows , how table gets values. example console.log(tablefor("pizza", journal)); , [76, 9, 4, 1]. how god's sake ?

the journal supplied book , looks : 

var journal = [   {"events":["pizza","exercise","weekend"],"squirrel":false},   {"events":["bread","pudding","brushed teeth","weekend","touched    tree"],"squirrel":false},   {"events":["carrot","nachos","brushed    teeth","cycling","weekend"],"squirrel":false},   {"events":["brussel sprouts","ice cream","brushed    teeth","computer","weekend"],"squirrel":false},   {"events":["potatoes","candy","brushed    teeth","exercise","weekend","dentist"],"squirrel":false},   {"events":["brussel sprouts","pudding","brushed    teeth","running","weekend"],"squirrel":false},   {"events":["pizza","brushed teeth","computer","work","touched    tree"],"squirrel":false},   {"events":["bread","beer","brushed    teeth","cycling","work"],"squirrel":false},   {"events":["cauliflower","brushed teeth","work"],"squirrel":false},   {"events":["pizza","brushed teeth","cycling","work"],"squirrel":false},   {"events":["lasagna","nachos","brushed teeth","work"],"squirrel":false},   {"events":["brushed teeth","weekend","touched tree"],"squirrel":false},   {"events":["lettuce","brushed     teeth","television","weekend"],"squirrel":false},   {"events":["spaghetti","brushed teeth","work"],"squirrel":false},   {"events":["brushed teeth","computer","work"],"squirrel":false},   {"events":["lettuce","nachos","brushed teeth","work"],"squirrel":false},   {"events":["carrot","brushed teeth","running","work"],"squirrel":false} ...etc

what understand event passed parameter , looks through array of objects in jounral see if it's present. how counting take place ? 

if (entry.squirrel) index += 2;

why +2 ? why not index += 3; or index += 4; ???

and why table[index] += 1; ???

for example first loop goes this, : console.log(tablefor("pizza", journal));

//flow i=0;

from first line above in journal, pizza present. 

     if (hasevent(event, entry)) index += 1;

so index incremented , becomes 1.it continues : 

     if (entry.squirrel) index += 2;

squirel false, nothing happens index.if squirel found, why +2 ???

then table[index] += 1 can't understand point.

can please break down me ? helpful training.

thank in advance.

the table array count of entries meet different criteria. table[3] count of entries both entry.squirrel hasevent(event, entry) true. table[2] count entry.squirrel true, table[1] count hasevent(event, entry) true, , table[0] count neither true.

so logic index starts @ 0. if hasevent(event, entry) true, add 1 it. if entry.squirrel true add 2 it. result if both true, end adding 3. , if neither true don't add anything, it's still 0.

then add 1 table[index] increment counter.


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