Question

I want to return an array when one of the elements matches an item within an array.

Is the below code the fastest way to loop through an array when a value matches in a javascript array of arrays?

Note : Welcome any suggestions to modify the variable relatedVideosArray to make it a different data structure for better performance.

var relatedVideosArray = [

["1047694110001"],
["1047694111001", "1019385098001","1020367665001","1020367662001", "1019385097001", "1020367667001"],
["1040885813001"],
["1019385094001", "1019385096001"], 
["952541791001", "952544511001", "952544512001", "952544508001", "952541790001","952580933001", "952580934001", "1051906367001"]                                        

]


function getRelatedVideos(videoClicked){

    var tempStoreArray = [];    
    var getCurrentId = videoClicked;    
    var relVideoslen = relatedVideosArray.length;

    for(var i in relatedVideosArray) {
        tempStoreArray = relatedVideosArray[i]; 
      for(var j in tempStoreArray){             
                if(tempStoreArray[j] == getCurrentId){                  
        return relatedVideosArray[i];                   
        }               
      }
    }       
}

Update: I initially thought of making a key of video ids and values as all the related ids, but I want to display the key as well as all the related ids if any of the ids within the value array are clicked. Hope this helps to explain the constraint I have.

Answer 1

Modern day browsers support Array indexOf.

For the people saying the array indexOf is slower, basic tests on speed.

var values = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20];

console.time("for");
for(var i=0;i<1000;i++){
  for(var j=0;j<=values.length;j++){
    if(values[j]===20) break;
  }
}    
console.timeEnd("for");

console.time("reverse for");
for(i=0;i<1000;i++){
  for(var j=values.length-1;j>=0;j--){
    if(values[j]===1) break;
  }
}
console.timeEnd("reverse for");


console.time("while");
for(i=0;i<1000;i++){
  var j=0;
  while (j<values.length){
    if(values[j]===20) break;
    j++;
  }
}
console.timeEnd("while");


console.time("reverse while");
for(i=0;i<1000;i++){
  var j=values.length-1;
  while (j>=0){
    if(values[j]===1) break;
    j--;
  }
}
console.timeEnd("reverse while");


console.time("indexOf");
for(var i=0;i<1000;i++){
  var x = values.indexOf(20);
}
console.timeEnd("indexOf");

console.time("toString reg exp");
for(var i=0;i<1000;i++){
  var x = (/(,|^)20(,|$)/).test(values.toString);
}
console.timeEnd("toString reg exp");

Two possible solutions:

var relatedVideosArray = [

["1047694110001"],
["1047694111001", "1019385098001","1020367665001","1020367662001", "1019385097001", "1020367667001"],
["1040885813001"],
["1019385094001", "1019385096001"], 
["952541791001", "952544511001", "952544512001", "952544508001", "952541790001","952580933001", "952580934001", "1051906367001"]                                        

]

//var getCurrentId = "1019385098001";
var getCurrentId = "1040885813001";


console.time("indexOf");
var tempStoreArray = [];
for(var i = relatedVideosArray.length-1; i>=0; i--){
     var subArr = relatedVideosArray[i];
     if(subArr.indexOf(getCurrentId)!==-1){
        tempStoreArray.push(subArr);
     }
}
console.timeEnd("indexOf");
console.log(tempStoreArray);




console.time("toString reg exp");
var tempStoreArray = [];
var re = new RegExp("(,|^)" + getCurrentId + "(,|$)");
for(var i = relatedVideosArray.length-1; i>=0; i--){
     var subArr = relatedVideosArray[i];
     if(re.test(subArr.toString())){
        tempStoreArray.push(subArr);
     }
}
console.timeEnd("toString reg exp");
console.log(tempStoreArray);