Nodejs Array Item Occurrence numberOfOccurrences(arr)

Method Source Code

//The numberOfOccurrences function must return the number of occurrences of an element in an array.var arr = [0,1,2,2,3];
//arr.numberOfOccurrences(0) === 1;
//arr.numberOfOccurrences(4) === 0;
//arr.numberOfOccurrences(2) === 2;
//arr.numberOfOccurrences("a") === 0;

Array.prototype.numberOfOccurrences = function (arr) {
    var elem = 0;
    for (var i = 0; i < this.length; i++) {
        if (this[i] === arr) {
            elem++;/*from   w w w.  j av  a 2  s .  co  m*/
        }
    }
    return elem;
};

Related

1. numberOfOccurrences( arg )

   Array.prototype.numberOfOccurrences = function( arg ) {
     var num = 0;
     this.forEach( function( e ){
       if ( arg === e ) { num++; }
     });
     return num;
   };
   var arr = [0,1,2,2,3,"a"];
   console.log( arr.numberOfOccurrences("a") );
   ...
   

2. numberOfOccurrences(chr)

   Array.prototype.numberOfOccurrences = function(chr) {
     return this.filter(function(x){ return x == chr; }).length;
   

3. numberOfOccurrences(desVal)

   Array.prototype.numberOfOccurrences = function(desVal) {
     var counter = 0;
     this.forEach(function(value){
       if(value === desVal){
         counter++;
     });
     return counter;
   };
   ...
   

4. numberOfOccurrences(el)

   Array.prototype.numberOfOccurrences = function (el) {
     var count = 0;
     this.forEach(function (item) {
       if (item === el) count++;
     });
     return count;
   

5. numberOfOccurrences(elem)

   Array.prototype.numberOfOccurrences = function(elem) {
     let obj = {};
     this.forEach(elem => elem in obj ? obj[elem]++ : obj[elem] = 1);
     return obj[elem] === undefined ? 0 : obj[elem]