fillArrayWithNums.js

/*
Example 1:

Input: nums = [1,2,3,4]
Output: [2,4,4,4]
Explanation: The first pair [1,2] means we have freq = 1 and val = 2 so we generate the array [2].
The second pair [3,4] means we have freq = 3 and val = 4 so we generate [4,4,4].
At the end the concatenation [2] + [4,4,4] is [2,4,4,4].
Example 2:

Input: nums = [1,1,2,3]
Output: [1,3,3]
 

Constraints:

2 <= nums.length <= 100
nums.length % 2 == 0
1 <= nums[i] <= 100
*/

//Answer//

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var decompressRLElist = function(nums) {
    let A = [];
    for (let i = 0; i < nums.length ; i+=2) {
A = A.concat(Array(nums[i]).fill(nums[i+1]))
};
    return A
};