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concatenation of array

Link :https://leetcode.com/problems/concatenation-of-array/

solution 1​

var getConcatenation = function (nums) {
  return [...nums, ...nums];
};

solution 2​

return nums.concat(nums);

solution 3​

var getConcatenation = function (nums) {
  let arr = [];
  let limit = nums.length * 2;
  let index = 0;
  for (let i = 0; i < limit; i++) {
    arr[i] = nums[index++];
    if (index == nums.length) {
      index = 0;
    }
  }
  return arr;
};