Exploring the "how to think about it" questions is truly rewarding for me, so please excuse the detailed explanation.
When approaching a problem like this, my initial step is to take a simplistic approach, focusing solely on the core logic without getting bogged down in unnecessary details (such as programming language specifics). By gaining a clear understanding of the problem at hand, you can more easily recognize relevant code snippets when it comes time to implement them.
Let's define "rows" within the context of a 2d grid. Consider the following code snippet:
var myArray = [["pat", "tom" , "john"], ["sam", "toby", "barbra"],
["william","jack", "janice"]];
Simplifying this, let's represent it as follows: g is "grid", r is "row", and c is "column":
g = r1 ( c1, c2, c3 )
r2 ( c1, c2, c3 )
r3 ( c1, c2, c3 )
The pattern here is quite straightforward. Moving on to the instruction to "move forward through the rows," I interpret this as starting from a given row and progressing either forward or backward to adjacent rows (note that ES6 provides handy tools for achieving this without external libraries, such as iterators).
Here is a basic code outline (there are more efficient ways to accomplish this task functionally, but considering your familiarity with JavaScript, I'll keep it simple):
// Assuming the need to find a row index based on a value.
// We only require the index, not the actual row itself.
// This step may be skipped for the first/last row,
// as their indices would be 0 and grid.length - 1 respectively.
var findRow = function ( val ) {
grid.forEach ( function ( row, row_i ) {
if ( row.find ( val ) {
return row_i;
}
}
}
// Proceeding to navigate through rows
// Using 0 and 1 as valid values for "next" and "previous"
// Alternatively, separate functions like "next" and "prev" could be implemented passing 0 and 1 to this function.
var navRow = function ( row_num, direction ) {
// Validating the direction parameter
var validDirections = [ 0, 1 ];
if ( ! validDirections.find ( direction ) ) {
console.log ( 'bad direction!!!' ) {
return;
}
// Ensuring the row number is within bounds
if ( ! (row_num >= 0 && row_num < grid.length) ) {
console.log ( 'bad row num!!!' );
return;
}
// Calculating the target row based on direction
// Utilizing falsy check due to direction being either 0 or 1
if ( direction ) {
row_num++;
} else {
row_num--;
}
// Handling out-of-bounds scenarios by wrapping around
if ( row_num < 0 ) {
row_num = grid.length - 1;
} else if ( row_num >= grid.length ) {
row_num = 0;
}
// Returning the updated index
return row_num;
}
Usage example:
var startIndex = findRow ( 'janice' );
// Note that startIndex might be undefined if no matching row is found!
// Be sure to handle such cases.
var newIndex = navRow ( startRow, 0 ); // move back or wrap to end
var newIndex = navRow ( startRow, 1 ); // proceed forward or wrap to start
Your initial row was represented as grid[ startIndex ], while the newly navigated row is now accessed using grid[ newIndex ].
This method eliminates the need for class or global variables to track the current index during navigation. The concept of newIndex essentially becomes akin to startIndex, hinting at possible recursion or generator/yield patterns. In any case, this approach proves advantageous.
It's worth noting that the provided code assumes a very simplistic grid structure. If your grid exhibits complexity like non-unique row values, duplicates, uneven rows, etc., further refinement and testing are necessary (although the outlined code should still serve its purpose effectively). Begin by outlining the process, verifying your logic and safeguards before delving into implementation.