Getting read property error undefined in node.js

Question

I am working on scraping part and i am getting the data well, but when I am iterating the array and trying to get the data throwing me TypeError: Cannot read property '3' of undefined

My code is:

  $('table#blob1 tr.insRow').filter(function(){
            var data = $(this);
            i = i + 1;
            bow_arr[i] = new Array(6);
            bow_arr[i][1] = data.children(1).text();
            bow_arr[i][2] = data.children(2).text();
            bow_arr[i][3] = data.children(3).text();
            bow_arr[i][4] = data.children(4).text();
            bow_arr[i][5] = data.children(5).text();
            bow_arr[i][6] = data.children(6).text();    
   })

Here i am creating two dimensional array and inserting the data into it. and i am able to get all the children values correctly and i have inserted all those data into the two dimensional array.

The filter function runs for 5 times since it is encountered five times.

 for(i=0;i<1;i++){
     console.log(bow_arr[i][3]+" - "+bow_arr[i][4]);
  }

The above code i am just trying to print the values but i am getting TypeError like this. TypeError: Cannot read property '3' of undefined

Unrelated tip: nobody uses the new Array(6) notation nowadays. It's lengthy and it's easy to use it wrong inadvertently. Just [] will do. — Álvaro González
– Álvaro González, Commented May 7, 2014 at 11:26

Ivan Drinchev · Accepted Answer · 2014-05-07 11:42:35Z

According your code, your iterator loop is written in a wrong way.

In your code you have

i = i + 1;

Which makes your array look like this :

bow_arr[0] === undefined; // equals true

bow_arr[1] === [ 'text from child 1', 'text from child 2' ... ]
bow_arr[2] === [ 'text from child 1', 'text from child 2' ... ]

And your iterator

for(i=0;i<1;i++) { ... }

Will iterate only 0 one time.

You have two possibilities. To fix your code or to fix your iterator

I choose to fix your iterator, which should look like :

for(i=1;i<bow_arr.length;i++){
   console.log(bow_arr[i][3]+" - "+bow_arr[i][4]);
}

Just to make sure you can also include a check to see if this item in the array is undefined.

for(i=1;i<bow_arr.length;i++) {
   if ( !bow_arr[i] || !bow_arr[i][3] || !bow_arr[i][4] ) continue;
   console.log(bow_arr[i][3]+" - "+bow_arr[i][4]);
}

Joakim M · Accepted Answer · 2014-05-07 11:39:55Z

As VisioN says you are indexing 0 but you have not entered anything into that post. Initiate i as 0 and you should be fine :). Move incrementation to end of filter function.

  var i = 0;

  $('table#blob1 tr.insRow').filter(function(){
            var data = $(this);
            bow_arr[i] = new Array(6);
            bow_arr[i][1] = data.children(1).text();
            bow_arr[i][2] = data.children(2).text();
            bow_arr[i][3] = data.children(3).text();
            bow_arr[i][4] = data.children(4).text();
            bow_arr[i][5] = data.children(5).text();
            bow_arr[i][6] = data.children(6).text();    
            i = i + 1;
   })

Fyi: You loop ONCE in the code below = What's the point of having a loop? :)

 for(i=0;i<1;i++){
     console.log(bow_arr[i][3]+" - "+bow_arr[i][4]);
  }

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