Question 53156 in Javascript Question posted in
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How to add an item at a random position in an array, javascript?

I have an array var arr = [1,2,3,4,5] and I want to add x at a random position in the array.

I tried this

let n = arr.length;
let randomIndex = Math.floor(Math.random() * arr.length);
for (let i = randomIndex; i < n + 1; i++) {
    arr[i+1] = arr[i];
    arr[randomIndex] = 'x';
}

The expected output after calling the function above was [1,2,’x’,3,4,5] or [‘x’,1,2,3,4,5] or [1,2,3,4,’x’,5] But it didn’t work. Any suggestion would help

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3

Answers


  1. 0

    Use splice to insert at at particular position. The idiom | 0 is equivalent to Math.floor() for positive numbers less than 2^31.

    Note that you need to use arr.length+1 to ensure that one of the possible the random positions can be after the last element of the original array.

    const arr = [1,2,3,4,5]

arr.splice((arr.length+1) * Math.random() | 0, 0, 'x')

console.log(arr)
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  2. 0 
    let arr = ['apple', 'pear', 'banana'];
arr[Math.floor(Math.random()*arr.length)]='tomato';
console.log(arr);
//tomato is not a fruit
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  3. 0

    It Should work perfectly.

    let arr = [1, 2, 3, 4, 5];
let n = arr.length;
let randomIndex = Math.floor(Math.random() * (n + 1)); // generate random index including the end of the array

arr.splice(randomIndex, 0, 'x'); // insert 'x' at random index

for (let i = n - 1; i > 0; i--) {
  let j = Math.floor(Math.random() * (i + 1)); // generate random index to swap with
  [arr[i], arr[j]] = [arr[j], arr[i]]; // swap elements at indices i and j
}

console.log(arr); // Output
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