Credit Card Checker - Making Sure the Company Returns Only Once

Hello All! Thank you so much those who have helped me thus far. I am now on the final instruction for Credit Card Checker Link. I would be so grateful for some more help! I’m using .push() and .pop() to ensure a credit card company isn’t repeated in an array but I’m getting a syntax error. It’s saying:
let companies = [‘Amex’, ‘Visa’, ‘MasterCard’, ‘Discover’];
^
SyntaxError: Identifier ‘companies’ has already been declared

Again, I’ll be forever grateful for your input!

// All valid credit card numbers
const valid1 = [4, 5, 3, 9, 6, 7, 7, 9, 0, 8, 0, 1, 6, 8, 0, 8];
const valid2 = [5, 5, 3, 5, 7, 6, 6, 7, 6, 8, 7, 5, 1, 4, 3, 9];
const valid3 = [3, 7, 1, 6, 1, 2, 0, 1, 9, 9, 8, 5, 2, 3, 6];
const valid4 = [6, 0, 1, 1, 1, 4, 4, 3, 4, 0, 6, 8, 2, 9, 0, 5];
const valid5 = [4, 5, 3, 9, 4, 0, 4, 9, 6, 7, 8, 6, 9, 6, 6, 6];

// All invalid credit card numbers
const invalid1 = [4, 5, 3, 2, 7, 7, 8, 7, 7, 1, 0, 9, 1, 7, 9, 5];
const invalid2 = [5, 7, 9, 5, 5, 9, 3, 3, 9, 2, 1, 3, 4, 6, 4, 3];
const invalid3 = [3, 7, 5, 7, 9, 6, 0, 8, 4, 4, 5, 9, 9, 1, 4];
const invalid4 = [6, 0, 1, 1, 1, 2, 7, 9, 6, 1, 7, 7, 7, 9, 3, 5];
const invalid5 = [5, 3, 8, 2, 0, 1, 9, 7, 7, 2, 8, 8, 3, 8, 5, 4];

// Can be either valid or invalid
const mystery1 = [3, 4, 4, 8, 0, 1, 9, 6, 8, 3, 0, 5, 4, 1, 4];
const mystery2 = [5, 4, 6, 6, 1, 0, 0, 8, 6, 1, 6, 2, 0, 2, 3, 9];
const mystery3 = [6, 0, 1, 1, 3, 7, 7, 0, 2, 0, 9, 6, 2, 6, 5, 6, 2, 0, 3];
const mystery4 = [4, 9, 2, 9, 8, 7, 7, 1, 6, 9, 2, 1, 7, 0, 9, 3];
const mystery5 = [4, 9, 1, 3, 5, 4, 0, 4, 6, 3, 0, 7, 2, 5, 2, 3];

// An array of all the arrays above
const batch = [valid1, valid2, valid3, valid4, valid5, invalid1, invalid2, invalid3, invalid4, invalid5, mystery1, mystery2, mystery3, mystery4, mystery5];


// Add your functions below:

const validateCred = array => {
  newArray =[];
  for (var i = array.length - 2; i >= 0; i -= 2)
{ 
  let doubleValue = array[i] * 2;
     if (doubleValue > 9) {
        doubleValue -= 9;
  }     newArray.push(doubleValue);
}
  
  for (var j = array.length - 1; j >= 0; j -=2) {
        newArray.push(array[j]);
  }
  return newArray.reduce((prv, cur) => prv + cur) % 10 === 0;
  };

  const findInvalidCards = cards => {
    const invalidNumbers = [];
      for (let j = 0; j < cards.length; j++) {
        let credCards = cards[j];
        if (!validateCred(credCards)) {
          invalidNumbers.push(credCards);
        }
      } return invalidNumbers;
    };

    const idInvalidCardCompanies = invalidCards => {
      const id = [];
      for (let i = 0; i < invalidCards.length; i++ ) {
      let company = invalidCards[i];
        if (company[0] === 3){
          id.push('Amex');
        } else if (company[0] === 4){
          id.push('Visa');
        } else if (company[0] === 5){
          id.push('Mastercard');
        } else if (company[0] === 6) {
          id.push('Discover');
        } else {
          console.log('Company not found');
        }
      }
    }; 
    
    const returnOnce = (id, companies) => {
      let companies = ['Amex', 'Visa', 'MasterCard', 'Discover'];
            if id.indexOf(companies) === -1 {
            id.push(companies);
          } else if id.indexOf(companies) > -1 {
            id.pop(companies);
          } return id;

    };
    
    
  




Since companies is a function parameter, it is already declared, so you don’t need to use let, const, or var when referencing it inside the function:

function someFunc(someParam) {
  someParam = 5;//here I don't need to use let, const or var, since someParam
  //is a function parameter.
  return someParam;

}

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