Add to array element

Question

I have an array, the value of the first element is 1.

Every time a user clicks a button, I want it to increase by 1. I have this written, but it's making the array element go from 1, to 11, to 111... and so on. How do I just get it to increase by 1. Like 1, 2, 3...

function addCake (){
 quantityArray[0] += 1;
 var cost= quantityArray[0] * 1.49;
 document.getElementById("cart").innerHTML += "<tr id="+"cakeTotal"+"><td>"+quantityArray[0]+"</td>Cake Donut</td><td>"+"$"+cost+"</td>";
}

• Itay: How and when are you initializing this array?

Answer 1

Change your code as below :

function addCake (){
 quantityArray[0]=parseInt(quantityArray[0]) + 1;
 var cost= parseInt(quantityArray[0]) * 1.49;
 document.getElementById("cart").innerHTML += "<tr id="+"cakeTotal"+"><td>"+quantityArray[0]+"</td>Cake Donut</td><td>"+"$"+cost+"</td>";
}

Answer 2

Try to convert it to int

quantityArray[0] = parseInt(quantityArray[0]);
quantityArray[0] += 1;

---

The problem I see is that you are initalizating the array items as "".

Why? if you set as 0, you can avoid the problem: http://jsfiddle.net/rgvaT/2/

quantityArray[0]=0;

• Dipesh Parmar: i think you need to edit it to parseInt(quantityArray[0]) because 1 is int by default.
• Ktown: this would probably work, but it starts at 0, so it's giving me NaN
• chris-l: @Ktown Ah! can you post some more code? like on a fiddle? It would be easier to write the precise code you need that way
• chris-l: @Ktown Edited the answer with your fiddle

Answer 3

You could try:

quantityArray[0]++;

This will also add 1 to your counter.

Answer 4

No need to call parseInt etc. Just initialize your quantityArray array properly:

var quantityArray = [];
quantityArray[0] = 0;
function addCake (){
 quantityArray[0]++;
 var cost = quantityArray[0] * 1.49;
 document.getElementById("cart").innerHTML += "<tr id="+"cakeTotal"+"><td>"+quantityArray[0]+"</td>Cake Donut</td><td>"+"$"+cost+"</td>";
}

• anubhava: @ktown: Dont initialize your array element like this: quantityArray[0]="";. As I suggested above make it quantityArray[0]=0;

Answer 5

Try this

quantityArray[0]=parseInt(quantityArray[0]) + 1;

• anubhava: Does 1 require parseInt?

Answer 6

var test = new Array();
 test[0] = 1;
 test[0] += 1;
 test[0] += 1;
alert(test[0]); // output is 3. Its working fine.

What you are doing is concatenating the "String" 1 with previous value of array.

To avoid that cast the value to int, using parseInt(). Something like this.

function addCake (){
 quantityArray[0] += parseInt(1, 10); // To decimal. It is very important
 var cost= quantityArray[0] * 1.49;
 document.getElementById("cart").innerHTML += "<tr id="+"cakeTotal"+"><td>"+quantityArray[0]+"</td>Cake Donut</td><td>"+"$"+cost+"</td>";
}

Answer 7

I guess you have initialized the array element as string. use below code to increment the element .

quantityArray[0] = parseInt(quantityArray[0]) + 1;

Answer 8

Here The Problem is with They datatype

In JavaScript, when you declare a variable by var x; It stores the variable as an object of type var.That is what causing the problem.

You need to Convert the object ( var ) to an integer to do mathematical operations by type casting. You can typecast using (Number) function. In other cases it consider + as an append operator and variables as String do append function.

The code will looks like this.

function addCake (){
 quantityArray[0] =(Number)quantityArray[0]+1;
 var cost= quantityArray[0] * 1.49;
 document.getElementById("cart").innerHTML += "<tr id="+"cakeTotal"+"><td>"+quantityArray[0]+"</td>Cake Donut</td><td>"+"$"+cost+"</td>";
}