[IMPORTANT] Javascript interview programs

Ques 1: Create a function named `customObjFlatten` which will take an pure nested object and return single level key value pair such as
      INPUT
          {
              a: 12,
              b: 15,
              c: {
                  d: 31,
                  e: {
                      f:51,
                      g: {
                          h: 64,
                          i: 99
                      }
                  }
              }
          }
       OUTPUT
          { a: 12, b: 15, c_d: 31, c_e_f: 51, c_e_g_h: 64, c_e_g_i: 99 }
          
       SOLUTION
          const blank = {};
          function flatten(obj, prefix=""){
              for(let key in obj){
                  let newKey = `${prefix}${key}`;
                  if(typeof(obj[key]) == 'object') {
                      return flatten(obj[key], `${newKey}_`)
                  } else {
                      blank[`${newKey}`] = obj[key]
                  }
              }
              console.log(blank)
          }
          flatten(obj1)
          
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Ques 2: Create a function `customArrFlatten` which will take a nested array and create single level array such that:
      INPUT
          [1,2,3,[4,5,[6],[7], [8,9,10,[11]]]]
      OUTPUT
          [1,2,3,4,5,6,7,8,9,10,11]
      SOLUTION
          const flatArr = []
          function customArrFlatten(arr){
              for(let i = 0; i < arr.length; i++){
                  if(Array.isArray(arr[i])) {
                      return customArrFlatten(arr[i])
                  } else {
                      flatArr.push(arr[i])
                  }
              }
          }
          customArrFlatten(arr)
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 Ques 2: Find the pairs in an array having sum = n
      INPUT
            arr = [ 1, 8, 45, 6, 10, 8 ];
            sum = 16
      OUTPUT
            (8.8), (10,6)
      SOLUTION
            let store = new Set();
            let leng = arr.length;

            for(let i = 0;i < leng;i++){
                let temp = n - arr[i];
                if(store.has(temp)){
                    console.log(`Pair: (${temp}, ${arr[i]})`);
                }
                store.add(arr[i])
            }