longest-common-prefix

var longestCommonPrefix = function(strs) {
   var common = "";
   var index = 0;

   if(strs.length == 0 || strs == "null"){
	   return common;
   }

   // split the first string of strs
   var string = strs[0].split("");

    // Loop over the stored string's letter 
   for(let i=0; string.length > i; i++){
   var letter = string[i];
     // Loop over the rest of the strings and compare the same indexies of each string 
	   for(let j=1; strs.length > j; j++){
		   if(letter != strs[j].charAt(index) || index > strs[j].length){
			   return common;
		   }
	   }
	common += letter;
	index++;

   }
     return common;
 };
 
 longestCommonPrefix(["flower","flow","flight"]) // return "fl"

Coding practice from Leet Code's "Longest Common Prefix" question.