Finding index of value in two dimensional array of objects in javascript

Question

I have a 2D array of objects like so:

[[{id: 123}, {id: 456}, {id: 789}], [{id: 111}, {id: 222}, {id: 333}], [{id: 444}, {id: 555}, {id: 666}], [{id: 777}]]

I need to find the index of the id at the top array level.

So if i was to search for and id property with value '222' i would expect to return an index of 1.

I have tried the following:

var arr = [[{id: 123}, {id: 456}, {id: 789}], [{id: 111}, {id: 222}, {id: 333}], [{id: 444}, {id: 555}, {id: 666}], [{id: 777}]],
 len = arr.length
 ID = 789;
for (var i = 0; i < len; i++){
 for (var j = 0; j < arr[i].length; j++){
 for (var key in o) {
 if (key === 'id') {
 if (o[key] == ID) {
 // get index value 
 }
 }
 } 
 }
}

Answer 1

Wrap your code in a function, replace your comment with return i, fallthrough by returning a sentinel value (e.g. -1):

function indexOfRowContainingId(id, matrix) {
 for (var i=0, len=matrix.length; i<len; i++) {
 for (var j=0, len2=matrix[i].length; j<len2; j++) {
 if (matrix[i][j].id === id) { return i; }
 }
 }
 return -1;
}
// ...
indexOfRowContainingId(222, arr); // => 1
indexOfRowContainingId('bogus', arr); // => -1

Answer 2

Since you know you want the id, you don't need the for-in loop.

Just break the outer loop, and i will be your value.

var arr = [[{id: 123}, {id: 456}, {id: 789}], [{id: 111}, {id: 222}, {id: 333}], [{id: 444}, {id: 555}, {id: 666}], [{id: 777}]],
 len = arr.length
 ID = 789;
OUTER: for (var i = 0; i < len; i++){
 for (var j = 0; j < arr[i].length; j++){
 if (arr[i][j].id === ID)
 break OUTER; 
 }
}

Or make it into a function, and return i.