TypeError: Cannot Read Property 'push' of undefined in two-dimensional array

Question

So, here, I am trying to create a two dimensional array; an array of arrays. However, whenever I try to push a value to the nested array, I receive the error seen in the title. In these for loops, the 'b' array is full of a list of strings, which are all received in a certain format, and the code then breaks it up and pushes it to the values in the 2-D array for further working.

var c = []

for(var u = 0; u < b.length; u++){
  c[u] = new Array(0);
  for(var y = 0; y < b[u].length; y++){
    c[u][y].push(b[u].substring(b[u].indexOf('\"'), b[u].indexOf(",")));
    b[u] = b[u].substring(b[u].indexOf(',') + 1);
  }
}

I've looked on the other solutions here on stackoverflow; Either I can't wrap my head around them, or they're not applicable here. I can't tell what's wrong here. Help, please.

Well for one thing, when the process starts, b.length is zero; at the start there's nothing in the arrays yet, so the outer loop will perform no iterations. — Pointy
– Pointy, Commented May 25, 2016 at 14:05
b already contains strings, filled by another loop. I'll clarify, sorry. — orlando marinella
– orlando marinella, Commented May 25, 2016 at 14:06
What are you trying to do? I'm almost sure there's a better way than a nested for loop and stateful calls to .push(). — Madara's Ghost
– Madara's Ghost, Commented May 25, 2016 at 14:08
It's hard to tell what sort of results you want, but it probably should just be c[u].push(...) instead of c[u][y].push(...). — Pointy
– Pointy, Commented May 25, 2016 at 14:09
It's interpreting an input in a list format, separated by commas. For some reason, where I'm getting it from insists on using a '"' around each element in the list. I'm going to be doing other things to these strings afterwards, though, I'm just trying to mince it into chunks. — orlando marinella
– orlando marinella, Commented May 25, 2016 at 14:10

zpul · Accepted Answer · 2016-05-25 14:11:04Z

2

var c = []

for(var u = 0; u < b.length; u++){
  c[u] = new Array(0);
  for(var y = 0; y < b[u].length; y++){
    // NOT WORKING
    // c[u][y].push(b[u].substring(b[u].indexOf('\"'), b[u].indexOf(",")));

    // WORKING
    c[u].push(b[u].substring(b[u].indexOf('\"'), b[u].indexOf(",")));

    // WORKING
    c[u][y] = b[u].substring(b[u].indexOf('\"'), b[u].indexOf(","));

    b[u] = b[u].substring(b[u].indexOf(',') + 1);
  }
}

answered May 25, 2016 at 14:11

zpul

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1 Comment

zpul Over a year ago

glad to know it helps.

Rohìt Jíndal · Accepted Answer · 2016-05-25 14:15:54Z

0

As you already declare an array b as blank without any value var b = [].

So, b.length will be 0.

Then this condition for(var u = 0; u < b.length; u++) will not execute and code will not work.

Update :

So, you can directly use :

c[u].push(b[u].substring(b[u].indexOf('\"'), b[u].indexOf(",")));

edited May 25, 2016 at 14:15

answered May 25, 2016 at 14:09

Rohìt Jíndal

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1 Comment

orlando marinella Over a year ago

b contains strings. Earlier, var b = [] was used as a placeholder for this question only. Apologies for the confusion.

cyberbit · Accepted Answer · 2016-05-25 14:17:12Z

0

I think the problem here is that you are trying to use .push on something that is already a value:

/**
 * c is an array: []
 */
var c = []

for (var u = 0; u < b.length; u++) {
  /**
   * c[u] is a subarray: [u: []]
   */
  c[u] = new Array(0);
  for (var y = 0; y < b[u].length; y++) {
    /**
     * c[u][y] is a value, currently undefined: [u: [y: ??]]
     */
    c[u][y].push(b[u].substring(b[u].indexOf('\"'), b[u].indexOf(",")));
    b[u] = b[u].substring(b[u].indexOf(',') + 1);
  }
}

For what you want, you use either of the following:

// Value (replace as needed)
var value = b[u].substring(b[u].indexOf('\"'), b[u].indexOf(","));

// Option 1
c[u][y] = value;

// Option 2
c[u].push(value);

answered May 25, 2016 at 14:17

cyberbit

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