javascript - Convert "pt" to "px" using regular expression - Stack Overflow

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In WYSIWYG editor, I have

<TABLE style="WIDTH: 162pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=216>

I can convert this to

<TABLE style="WIDTH: 162px; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=216>

using

"wysiwygdata".replace(/pt/g ,"px");

Is there any way to change associated value of pt to the value of px using regex.

162pt might be 162*96/72px.

Looking for your help.

In WYSIWYG editor, I have

<TABLE style="WIDTH: 162pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=216>

I can convert this to

<TABLE style="WIDTH: 162px; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=216>

using

"wysiwygdata".replace(/pt/g ,"px");

Is there any way to change associated value of pt to the value of px using regex.

162pt might be 162*96/72px.

Looking for your help.

• javascript
• regex

Share Improve this question Follow asked Dec 21, 2010 at 6:52 NazmulNazmul 7,2181212 gold badges5353 silver badges6464 bronze badges 3

• 2 I don't think you can do math with regex. – BoltClock Commented Dec 21, 2010 at 6:55
• 1 @BoltClock: No, but you can with String#replace and a callback. :-) – T.J. Crowder Commented Dec 21, 2010 at 6:59
• 96/72 came from stackoverflow./questions/139655/… – Nazmul Commented Dec 21, 2010 at 7:10

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 20

You can use a regular expression for this, where you feed a function into String#replace:

s = /* ...the data... */;
s = s.replace(/([0-9]+)pt/g, function(match, group0) {

    return Math.round(parseInt(group0, 10) * 96 / 72) + "px";
});

Live example

When you supply a function for the second argument of replace, it gets called for each match, with the plete match as the first argument, and then the value of any capture groups for subsequent arguments; the return value is used as the replacement. So above I'm using a capture group to capture the number, and then doing the math and returning the new string.

You might need or want to adjust the regex a bit to make sure it fits your data (possible spaces between the number and the units, possibly the i flag so it matches "PT" as well as "pt", etc.), but that's the fundamental approach.

In addition to T.J. Crowder solution: Since pt values are often non-integer (for example 237.36pt) it would be very useful to change regexp to match numbers without and optionally with decimal point, otherwise this regexp match fraction part only (i.e. 36pt in our example) and callback will produce incorrect value. This regexp should fix that issue:

/([0-9]*\.?[0-9]+)pt/g

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