Subtract a number from a variable

Question

I'm trying to subtract from revlength each time the loop occurs. eg if there are 2 'A Google user' posts then subtract 2 from revlength

this is what I tried.

var revlength = place.reviews.length;
if(place.reviews[index].author_name == 'A Google User') {
    $("#revnum").html(revlength--);
} 

upon adding to the script, the code does not work for

$.each(place.reviews, function (index, value) {
        if (place.reviews[index].text.length != 0) {
            if (place.reviews[index].text.length == 0) {
                $("#revnum").html(--place.reviews.length);
            }
            if (place.reviews[index].author_name == 'A Google User') {
                $("#revnum").html(--place.reviews.length);
                var imgid = '<img src="img/gplus.gif" width="50" height="50">';
            } else {
                $("#revnum").html(revlength);
                var imgid = '<img src="img/user.gif" width="50" height="50">';
            }

Answer 1

try this..

change

$("#revnum").html(revlength--);//you are doing post-decrement

to

$("#revnum").html(--revlength);//you need to change it pre-decrement.

If other parts are going right , then it will work sure.

Explanation:

--i and i-- where the position of the -- determines whether one is subtracted before or after the value is used.

if i-- the value will be used before decremented. if --i the value will be used after decremented.

Answer 2

Turning my comment (that appears to have worked) into an answer:

You need to actually decrement place.reviews.length .

if(place.reviews[index].author_name == 'A Google User') {
    $("#revnum").html(place.reviews.length--);
} 

Your original code was only decrementing a temporary variable revlength which was not persistent because you would just reload that variable from place.reviews.length each time. Thus place.reviews.length never got decremented.

---

By way of explanation, perhaps you were under the impression that after doing:

var revlength = place.reviews.length; 

That when you then did:

revlength--

that it would also decrement place.reviews.length , but that is not the case. revlength is a new variable that was set to have the value of place.reviews.length , but when you do revlength-- , that only changes that variable and doesn't have any effect on place.reviews.length . So, for the decremented value to persist, you need to decrement place.reviews.length .

Answer 3

I think this is what you want:

var revlength = $.grep(place.reviews, function (val) {
    return val.author_name !== 'A Google User';
}).length;
// alert(revlength);
// console.log(revlength);

Answer 4

Try this one,

var revlength = place.reviews.length;
revlength =  parseInt(revlength.toString());
if(place.reviews[index].author_name == 'A Google User') {
revlength--;
$("#revnum").html(revlength);
}