ReactJS tutorial code ported ES6 Code not working

Question

In ReactJS tutorial has a tutorial on building a tic tac toe game with React. There's this function that checks to see if a winning move is made.

function calculateWinner(squares) {
  const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let i = 0; i < lines.length; i++) {
    const [a, b, c] = lines[i];
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
}

it works but the for loop could be improved to use for x in lines like so

function calculateWinner(squares) {
  const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let line in lines) {
    const [a, b, c] = line;
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
}

but when I tried that it didn't find a winning so I resorted to the older code.

I'm not sure why though the second edit failed.

Konrad Klimczak · Accepted Answer · 2018-06-15 09:38:12Z

2

function calculateWinner(squares) {
    const lines = [[0, 1, 2], [3, 4, 5], [6, 7, 8], [0, 3, 6], [1, 4, 7], [2, 5, 8], [0, 4, 8], [2, 4, 6]];
    for (let line in lines) {
        console.log(line);
        const [a, b, c] = line;
        if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
            return squares[a];
        }
    }
    return null;
}

Run this code. Your line variable is index of array, not inner array (e.g. [0, 1, 2]).

EDIT:

As kristaps mentioned in comment proper solution is let line of lines (of instead of in).

edited Jun 15, 2018 at 9:38

answered Jun 15, 2018 at 9:30

Konrad Klimczak

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2 Comments

kristaps Over a year ago

Your code still says let line in lines, did you mean let line of lines?

Konrad Klimczak Over a year ago

I just pointed out why the code did not work properly. You are right.

manan5439 · Accepted Answer · 2018-06-15 09:50:45Z

0

here in your first code you are using for loop which can excess 2d array in proper way example below program will produce out put like

const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let i = 0; i < lines.length; i++) {
    const [a, b, c] = lines[i];
    console.log(lines[i]);
    }

and also for each loop is use for excess each element at a time for example below program will produce output like

    1
    2
    3

as it

const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let line in lines) {
    const [a, b, c] = line;
    console.log(line)
    }

i think you can understand what happened here

answered Jun 15, 2018 at 9:50

manan5439

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2 Comments

Sam B. Over a year ago

yes and to return the content not the index it should be for (let line of lines)

manan5439 Over a year ago

yah that a point for each loop is use for each element at a time

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