Javascript how can I calculate total price in an array of items? -

i'm new js , have cart in webstore making javascript assignment, , can't total price working displays on webpage when user clicks on items add cart. here array of items, appreciated, thank you

var cart; var items = new array(); //create array store items items[0] = "greatest hits cd", 10; items[1] = "girls cd", 10; items[2] = "shirt1", 20; items[3] = "mask tee", 20; items[4] = "crewneck", 25; items[5] = "tour poster", 9; 

and here display function

this.display = function () {   this.holder.innerhtml = "";   this.totalprice = 0;  (var i=0; i<this.quantities.length; i++) {   if (this.quantities[i] > 0) {   this.totalprice += this.quantities[i]*this.items[i];  var elm = document.createelement('div');   elm.innerhtml = "<span class='name'>"+this.items[i]+" \</span><span class='quantity'>quantity: "+this.quantities[i]+"</span>";   this.holder.insertbefore(elm, null);       }   }  var elm = document.createelement('div');   elm.innerhtml = "<span class='price'>total price: $"+this.totalprice+" </span>";  this.holder.insertbefore(elm, null);   document.getelementbyid('quantities').value = cart.quantities;  document.getelementbyid('items').value = cart.items;      } 

you trying create associative array (key/value pairs), isn't how standard arrays work in javascript.

instead, create array of objects store data. each "record" persisted object , objects each common set of property names (prop1 , prop2 in example). can loop through array of objects , upon each iteration, grab property interested in (prop2) in case.

var items = new array(); //create array store items    // each item in array store object 2 properties  // object literal syntax: {propertyname : propertyvalue, propertyname : propertyvalue, etc.}  items[0] = {prop1:"greatest hits cd", prop2:10};  items[1] = {prop1:"girls cd", prop2:10};  items[2] = {prop1:"shirt1", prop2:20};  items[3] = {prop1:"mask tee", prop2:20};  items[4] = {prop1:"crewneck", prop2:25};  items[5] = {prop1:"tour poster", prop2:9};    var sum = null;   // place store total cost      // javascript array.prototype specifies built-in method called  // foreach takes function argument. function  // automatically passed 3 arguments , executed each element   // in array.  items.foreach(function(value, index, arry){   sum += value.prop2;  });    console.log(sum);