Javascript can't convert undefined to object - Stack Overflow

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I have the following code

for(i = 0; i < num; i++) {
    var yPos = 10*i;
    var numCells = wid/30;

    for(j = 0; j < numCells; j++) {
        blocks[i][j] = 1;
    }                       
}

With

blocks = new Array();

However, when I execute the code I receive an error stating that:

can't convert undefined to object

Any ideas? :/

I have the following code

for(i = 0; i < num; i++) {
    var yPos = 10*i;
    var numCells = wid/30;

    for(j = 0; j < numCells; j++) {
        blocks[i][j] = 1;
    }                       
}

With

blocks = new Array();

However, when I execute the code I receive an error stating that:

can't convert undefined to object

Any ideas? :/

• javascript

Share Improve this question Follow edited Dec 9, 2012 at 13:30 Henrik Aasted Sørensen 7,1671111 gold badges5454 silver badges6464 bronze badges asked Dec 9, 2012 at 13:27 MrDMrD 5,0841212 gold badges5454 silver badges9595 bronze badges 1

• 1 I suspect you need to declare blocks to be a 2D array. Try [this question][1]. [1]: stackoverflow./questions/966225/… – chooban Commented Dec 9, 2012 at 13:30

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2 Answers 2

Sorted by: Reset to default 4

var blocks = [];
for(i = 0; i < num; i++) {    
    var yPos = 10*i;
    var numCells = wid/30;
    blocks[i] = []; // here is a fix

    for(j = 0; j < numCells; j++) {
        blocks[i][j] = 1;
    }
}

In your particular case, since all the rows are initialised to be the same (a series of 1s), you can also do

var blocks = new Array(),
    blockRow = new Array();
for (var i = 0; i < numCells; i++) {
    blockRow.push(1);
}
for (var i = 0; i < num; i++) {
    blocks.push(blockRow.slice());  // slice() makes a copy of blockRow
}

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