2D Javascript Arrays Not Returning Correct Length of "Second Dimension Arrays"

Question

I'm trying to dynamically create a "2D" array in Javascript, but it's more of an array of arrays, obviously. Each array in the array (which I will here on call a "second dimension array") is dynamically allocated based on a file the user uploads. The file is formatted:

Integer representing the number of lines in the drawing the file represents.

Integer representing the number of coordinates which make up a line of that drawing.

The coordinates in that line, each pair separated by a newline.

Another integer representing the number of coordinates in the next line in the drawing.

The coordinates in that line, each pair separated by a newline.

...etc.

For example:

3

5.0 2.0

3.4 6.7

7.8 9.6

6

5.0 2.0

3.4 6.7

7.8 9.6

8.9 7.8

9.6 4.3

3.7 2.7

4

4.0 4.0

7.8 5.0

3.8 8.3

2.1 7.6

You get the idea.

Here's my code to parse the file after it has been converted to a string:

function parseDat(contents) {
    var dirtyArray = contents.split("\n");
    var fileArray = dirtyArray.filter(function (n) { return (n !== undefined && n !== null && n !== ""); });


        var lineArray = new Array(parseInt(fileArray[i], 10) + 1);
        lineArray[0] = fileArray[i];

        i++;

        for(var j = 1; j < lineArray.length; j++) {
            lineArray[j] = new Array(fileArray[i]);
            console.log(fileArray[i]);
            console.log("2d array length = " + lineArray[j].length);
            i++;
            for(var k = 0; k < lineArray[j].length; k++, i++) {
                lineArray[j][k] = fileArray[i];
            }

        }

        return lineArray;


}

Basically, I check to see the length the second dimension array should be, which in the example file thing I gave should be 3 for the first line. console.log(fileArray[i]) returns the correct number, but when I use lineArray[j].length, for some reason, the answer is always 1. I've checked lots of other sources for 2D arrays in Javascript and this method of checking the second dimension array's length always works for them.

Please help, I know it's probably just some dumb mistake I'm making.

I'm an idiot and did not convert my strings into integers. Therefore I was setting my arrays equal in length to the string "3" (which is 1 long) instead of being 3 long. — Jade Strider
– Jade Strider, Commented Feb 2, 2020 at 4:21

funky · Accepted Answer · 2020-02-02 03:52:23Z

1

Maybe you can "ignore" the problem. If console.log(fileArray[i]) really does give the correct number, you could just go for this in your following for-statement:

for(var k = 0; k < lineArray[i]-1; k++, i++) {
    lineArray[j][k] = fileArray[i];
}

-1 because you increment it with i++ beforehand. Or you just declare a new var before incrementing and use that in your for-statement. Might be a bit of a lazy cheaty way out, but your code might work just as intended.

answered Feb 2, 2020 at 3:52

funky

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Jade Strider · Accepted Answer · 2020-02-02 04:26:56Z

0

I'm an idiot and did not convert my strings into integers. Therefore I was setting my arrays equal in length to the string "3" (which is 1 long) instead of being 3 long. The solution was to change

lineArray[j] = new Array(fileArray[i]);

to

lineArray[j] = new Array(parseInt(fileArray[i], 10));

answered Feb 2, 2020 at 4:26

Jade Strider

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