Question

What is the most portable way to delete element from multidimensional sparse array in javascript?

Will following work well if rows can be undefined sometimes?

if( content[row] ) {
    delete content[row][col];
}

Will this work and will it be better?

if( r=content[row] ) {
    delete r[col];
}

Answer 1

It depends. delete will leave an empty space in the array where the element was, like this:

var arr = [0, 1, 2, 3];
delete arr[1];
arr; // [0, undefined, 2, 3]

To remove an element from an array without leaving a hole, you should use splice():

arr.splice(1, 1); // Start deleting at index 1, delete one element
arr; // [0, 2, 3]

Both of your examples work just fine — if content[row] doesn’t exist, the body of the if statement won’t be evaluated.