Get Random and Unused Index Number Repeatedly For An Array (Maximum call stack error)-CodePudding

I am trying to write a simple "getRandomIndex" function to return a random and unused index number for a given array but I get "Maximum call stack size exceeded" error at let rndIdx = Math.floor(Math.random() * (arr.length - 0)) 0;.

const arr = [81, 33, 45, 22, 97, 19, 60];
const usedIndexes = []; // I am trying to store used indexes here

function getRandomIndex() {
  let rndIdx = Math.floor(Math.random() * (arr.length - 0))   0;
  
  if(usedIndexes.includes(rndIdx)) {
    getRandomIndex();
    return;
  } else {
    usedIndexes.push(rndIdx);
  }

  return rndIdx;
}

// if the array length is more than 10, I always get "call stack size exceed" error.
for(let i = 0; i < arr.length; i  ) {
  // I need to use all elements in the array eventually
  console.log(getRandomIndex());
}

What I am missing?

CodePudding user response：

You must check that the length of the array allows for different unused numbers.

if (usedIndexes.length>=arr.length) {
  return null
}

CodePudding user response：

You need to return the output of getRandomIndex() rather than calling it, dumping the output, then returning nothing (which gives you undefined)

Fixed Code

const arr = [81, 33, 45, 22, 97, 19, 60];
const usedIndexes = []; // I am trying to store used indexes here

function getRandomIndex() {
  let rndIdx = Math.floor(Math.random() * (arr.length - 0))   0;
  
  if(usedIndexes.includes(rndIdx)) {
    // used to be
    // - getRandomIndex();
    // - return;
    return getRandomIndex();
  } else {
    usedIndexes.push(rndIdx);
  }

  return rndIdx;
}

// if the array length is more than 10, I always get "call stack size exceed" error.
for(let i = 0; i < arr.length; i  ) {
  // I need to use all elements in the array eventually
  console.log(getRandomIndex());
}

Output