Question

I am trying to do something I though would be really simple. add the value of 1 to a number.

However the number was plain text and things are getting a little confusing. As you may be able to guess, I am fairly new to this.

My goal is to add 1 point to an existing score, the score has one decimal place, eg 1.3.
So the desired result after adding a point is 2.3. However The current script I wrote is returning adds a point to the second decimal place and I don’t understand why.

Thanks for the help.

var getPoints = parseInt($('.awesome-points').text(), 10).toFixed(1);
alert(getPoints);
var addPoint = 1;
var newScore = getPoints + addPoint;
$('.awesome-points').text(newScore);

Mark

Answer 1

.toFixed() returns a string (see the MDN documentation), that’s why getPoints + addPoint performs string concatenation, not addition.

Call that method after you performed the addition:

// unary + converts any numerical string to a number (no matter whether float
// or int)
var getPoints = +$('.awesome-points').text();
var newScore = getPoints + 1;
$('.awesome-points').text(newScore.toFixed(1));

Or more concise :

$('.awesome-points').text(function(i, val) {
    return (+val + 1).toFixed(1);
});

How this works:

Instead of passing a value to .text(), you can pass a function. This function will be executed for each of the selected elements. The first argument passed to the function is the index of the element in the set of selected elements and the second argument is the current text content. The return value will be set as new text content.
This is a good way to read and write the text content, without invoking .text() twice.

(+val + 1).toFixed(1) is evaluated as follows: First val is converted to a number through the unary plus (+val) and then increased by one (+ 1). .toFixed(1) is called on the result of that operation.

+val will return NaN if the text cannot successfully be converted into a number. I assume this won’t happen in your case, but this can easily be dealt with with the expression

return ((+val || 0) + 1).toFixed(1); 

That means, in case +val evaluates to false (which includes NaN), we use 0 instead. It’s a common pattern in JavaScript, see also What does "options = options || {}" mean in Javascript?.