What would be ideal replacement for nested for loops in terms of performance and ease of reading code, if I have over 8 for loops (besides two for loops) where I'm forming two array lists that I use to conclude to only one if statement in order to produce a result.

The database has multiple rows like:

{
   id: 12345
   creator: "John"
   number: 2.5
   type: 1
}

{
   id: 45678
   creator: "Alex"
   number: 2.0
   type: 2
}

// create array of elements with type:1
chat.find({"type":1}).toArray(function(err, res){
   const array1_id = [];
   const array1_creator = [];
   const array1_number = [];
   
   // form array for each element
   for(a=0;a<res.length;a  ){
      array1_id.push(res[a].id);
      array1_creator.push(res[a].creator);
      array1_number.push(res[a].number);
   }
   
   // create array of elements with type:2
   chat.find({"type":2}).toArray(function(err, res){
      const array2_id = [];
      const array2_creator = [];
      const array2_number = [];

      // form array for each element
      for(b=0;b<res.length;b  ){
         array2_id.push(res[a].id);
         array2_creator.push(res[a].creator);
         array2_number.push(res[a].number);
      }

      outerloop: for(c=0;c<array1_id.length;c  ){ // id (type: 1 row)

         var resNum1_id = array1_id[c];
         
         for(c1=0;c1<array1_creator.length;c1  ){ // creator (type: 1 row)
            var resNum1_creator = array1_creator[c1];

            for(c2=0;c2<array1_number.length;c2  ){ // number (type: 1 row)
               var resNum1_number = array1_number[c2];

               innerloop: for(d=0;d<array2_id.length;d  ){ id (type: 2 row)
                  var resNum2_id = array2_id[d];

                  for(d1=0;d1<array2_creator.length;d1  ){ creator (type: 2 row)
                     var resNum2_creator = array2_creator[d1];

                     for(d2=0;d2<array2_number.length;d2  ){ // number (type: 2 row)
                        var resNum2_number = array2_number[d2];

                        // find rows where condition is true
                        if(resNum1_number>=resNum2_number){
                           console.log
                             resNum1_id 
                             resNum1_creator 
                             resNum1_number 
                             "\n" 
                             resNum2_id 
                             resNum2_creator 
                             resNum2_number                              
                           );
                           break outerloop;
                        }
                        
                     }
                  }
               }
            }
         } 
      }

   });
});

CodePudding user response：

Just use two loops to loop over the two result arrays, comparing the num values from each.

// create array of elements with type:1 
chat.find({
    "type": 1
  })
  .toArray(function(err, res1) {
    // create array of elements with type:2
    chat.find({
        "type": 2
      })
      .toArray(function(err, res2) {
        for (let i = 0; i < res1.length; i  ) {
          for (let j = 0; j < res2.length; j  ) {
            if (res1[i].num >= res2[j].num) {
              console.log(res1[i].id   res1[i].creator   res1[i].num   "\n"   res2[i].id   res2[i].creator   res2[i].num);
              return;
            }
          }
        }
      });
  });