i have a 2D array "grid" in javascript, i want to prevent "the undefined of undefined error " and returning a simple "undefined", when the index of the first array is less than 0, this is my script:
let top = grid[this.posX][this.posY - 1];
let right = grid[this.posX + 1][this.posY];
let bottom = grid[this.posX][this.posY + 1];
let left = grid[this.posX - 1][this.posY];
if (top && !top.visited) neighbors.push(top);
if (right && !right.visited) neighbors.push(right);
if (bottom && !bottom.visited) neighbors.push(bottom);
if (left && left && !left.visited) neighbors.push(left);
here is the solution that works but i want to nkow if there is a better way to do it with less code:
let left, right, top, bottom;
let xm = this.posX - 1;
let xp = this.posX + 1;
let ym = this.posY - 1;
let yp = this.posY + 1;
if (xm < 0) {
left = undefined;
} else {
left = grid[xm][this.posY];
}
if (xp > rows) {
right = undefined;
} else {
right = grid[xp][this.posY];
}
if (ym < 0) {
top = undefined;
} else {
top = grid[this.posX][ym];
}
if (yp > cols) {
bottom = undefined;
} else {
bottom = grid[this.posX][yp];
}
Thanks in advance
You could add a check just before this code to detect out of bounds on posX.
if(!grid[this.posX - 1] || !grid[this.posX + 1])
return undefined;
I'm not sure what your grid contains, you might want to explicitly check for undefined instead of using the !
if you grid could contain 0s which are also falsy.
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