How to use .indexOf inside a for of loop in js-CodePudding

I'm a beginner to Javascript working on my first project: Tic Tac Toe!

I'm trying to write a function that will use a for/of loop to look through all the spaces on the game board and return an array of numbers corresponding with the index of any space that has an X in it.

Here are my variables:

var s = '_'
var x = 'X'
var O = 'O'
var spaceArr = [s,s,s,x,s,s,s,s,x]

spaceArray is the game board, with random x's in it for now. Here is my attempt at the function

function spaceChecker(array){
    let currGame = []
    for (var element of array){
        if (element==='X')    
    currGame.push(array.indexOf(element))
    }
return currGame
} 
console.log (spaceChecker(spaceArr))

It currently returns:

[ 3, 3 ]

How can I get .indexOf to update each time the for/of loops? Thanks!

CodePudding user response：

You have used indexOf which will return the first index of the X every time you are searching for X. If you want to use for..of loop then you have to track the index at which you are on.

var s = "_";
var x = "X";
var O = "O";
var spaceArr = [s, s, s, x, s, s, s, s, x];

function spaceChecker(array) {
  let currGame = [];
  let index = 0;
  for (var element of array) {
    if (element === "X") {
      currGame.push(index);
    }
    index  ;
  }
  return currGame;
}
console.log(spaceChecker(spaceArr));

ALTERNATE SOLUTION ⬇

You can just use reduce here to get the index of the X in an array

var s = "_";
var x = "X";
var O = "O";
var spaceArr = [s, s, s, x, s, s, s, s, x];

function spaceChecker(array) {
  return array.reduce((acc, curr, index) => {
    if (curr === "X") acc.push(index);
    return acc;
  }, []);
}
console.log(spaceChecker(spaceArr));

CodePudding user response：

As you do not need to return anything from the loop you can use forEach loop.

forEach((element, index) => {
   // if condition met push index in custom array
});

CodePudding user response：

The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

So your code will always return 3 because that will be the first index where X is found on every iteration.

It's much easier to use a basic for/loop and push the index of the current iteration into currGame when X is found.

const s = '_';
const x = 'X';
const O = 'O';

const spaceArr = [s, s, s, x, s, s, s, s, x];

function spaceChecker(array) {
  const currGame = [];
  for (let i = 0; i < array.length; i  ) {
    if (array[i] === 'X') currGame.push(i);
  }
  return currGame;
}

console.log(spaceChecker(spaceArr));