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What are these regex supposed to do?

The html includes a span tag with id="productPrice" which wraps around a price with currency symbol, and the in-page javascript includes a variable called baseprice which is set to be the innerHTML of productPrice and therefore includes the currency symbol.

Can you tell me please what does the regex do in the following code?
document.getElementById('productPrice').innerHTML = baseprice.replace(/[+-]*(d+).(d+)/, total.toFixed(2));

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The next alternative code is an extended version of the one above; Can you tell me please what does the next regex do?
document.getElementById('productPrice').innerHTML = baseprice.replace(/[+-]*(d+).(d+)/, total.toFixed(2).replace(/(d)(?=(d{3})+.)/g, "$1,"));

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The code above does not seem to work, the following does except that it loses the currency symbol:
document.getElementById('productPrice').innerHTML = total.toFixed(2);

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ncw
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ncw
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Derek JensenCommented:
baseprice.replace(/[+-]*(d+).(d+)/, total.toFixed(2));

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Okay so what's happening here is within the baseprice var it is:
[+-]*    // Looking for any plus or minus symbols (or possibly both or neither)
(d+)     // then, looking for at least one consecutive digits (and storing it in capture group $1)
.          // then it's looking for any single char (I'm thinking they meant to put \. to look specifically for a period char)
(d+)     // and finally it's looking for another consecutive string of at least one digit (stored in $2)
, total.toFixed(2)    // And, upon finding a match, replacing the entire matched group with total.toFixed(2) -- which also renders the capture groups unnecessary.

baseprice.replace(/[+-]*(d+).(d+)/, total.toFixed(2).replace(/(d)(?=(d{3})+.)/g, "$1,"));

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What's happening here is...well no wonder it's not working...

Okay so what the designer was *trying* to accomplish is to find any three consecutive digits and place a comma after it. The only way I was able to accomplish this correctly using regexes was by using two of them, as demonstrated here, although I'm convinced there's an easier way to do it.

There is no regex replace happening here, so of course it would not be inserting any commas :-)
document.getElementById('productPrice').innerHTML = total.toFixed(2);

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Sar1973Commented:
I suggest you to take a look to W3 schools tutorials (http://www.w3schools.com/js/js_obj_regexp.asp and http://www.w3schools.com/jsref/jsref_obj_regexp.asp). Th ToFixed JS function converts a number to a string, keeping the number of decimals you want (see http://www.w3schools.com/jsref/jsref_tofixed.asp).
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Derek JensenCommented:
@ncw wasn't asking what .toFixed() did, he asked what the regexes did, so I explained it. total.toFixed(2) was in the replace argv of .replace(). :-)
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ncwAuthor Commented:
Many thanks!
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