dynamically creating a regex with forward slashes in javascript

Question

Im trying to match lines that have this format. Writing a static regEx is fine but I need to do this using 2 variables to create the regex dynamically.

I cant seem to get how to escape the forward brackets properly ive tried escaping them, not escaping them and even double escaping them (just for the heck of it) but fireBug shows the actual regEx being created the same no mater how I do itand it doesnt match my input.

Lines to match look like this: 9.SSRDOCSWSHK1/////23NOV96/M//YEUNG/WINSTON/JEREMY-5.1

What Ive tried:

var regString ='\\d{1,2}.SSRDOCS[0-9A-Z]{2}HK1[/]{5}\\d\\d[A-Z]{3}\\d\\d/[MF]//'+curGstNme+'([/A-Z]+)?-'+pax.slice(0,1)+'\.'
var namedGdocRegEx = new RegExp(regString,"g");

FireBug gives RegExp /\d{1,2}.SSRDOCS[0-9A-Z]{2}HK1[\/]{5}\d\d[A-Z]{3}\d\d\/[MF]\/\/CASTANEDA\/HAZEL([\/A-Z]+)?-1./g

---------------------------

var regString ='\\d{1,2}.SSRDOCS[0-9A-Z]{2}HK1[\/]{5}\\d\\d[A-Z]{3}\\d\\d\/[MF]\/\/'+curGstNme+'([\/A-Z]+)?-'+pax.slice(0,1)+'\.'
var namedGdocRegEx = new RegExp(regString,"g");

FireBug gives RegExp /\d{1,2}.SSRDOCS[0-9A-Z]{2}HK1[\/]{5}\d\d[A-Z]{3}\d\d\/[MF]\/\/CASTANEDA\/HAZEL([\/A-Z]+)?-1./g

---------------------------

var regString ='\\d{1,2}.SSRDOCS[0-9A-Z]{2}HK1[\\/]{5}\\d\\d[A-Z]{3}\\d\\d\\/[MF]\\/\\/'+curGstNme+'([\\/A-Z]+)?-'+pax.slice(0,1)+'\.'
var namedGdocRegEx = new RegExp(regString,"g");

FireBug gives RegExp /\d{1,2}.SSRDOCS[0-9A-Z]{2}HK1[\/]{5}\d\d[A-Z]{3}\d\d\/[MF]\/\/CASTANEDA\/HAZEL([\/A-Z]+)?-1./g

anubhava · Accepted Answer · 2014-01-06 11:04:29Z

1

In regex you need to escape the DOTs since DOT will mean any character.

Use this regex:

regString ='\\d{1,2}\\.SSRDOCS[0-9A-Z]{2}HK1/{5}\\d\\d[A-Z]{3}\\d\\d/[MF]//'+ curGstNme + '([/A-Z]+)?-' + pax.slice(0,1) + '\\.';

answered Jan 6, 2014 at 11:04

anubhava

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Wesley Smith Over a year ago

nice catch, I missed that one

Wesley Smith · Accepted Answer · 2014-01-06 11:09:24Z

0

Actually the problem was elsewhere. Apparently fireBug just shows the created regex (in the "watch" panel) with the escaping sashes visible. This made me think the regex was not being created correctly.

answered Jan 6, 2014 at 11:09

Wesley Smith

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Stephan · Accepted Answer · 2014-01-06 11:17:06Z

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Your regex could be reduced like this:

var regString ='\\d{1,2}\\.SSRDOCS[0-9A-Z]{2}HK1/{5}\\d{2}[A-Z]{3}\\d{2}/[MF]//'+curGstNme+'([/A-Z]+)?-'+pax.slice(0,1)+'\.'

What did I change ?

\\d\\d can be replaced efficiently with \d{2}.
. replaced with \\. for matching exactly dot.
[/]{5} replaced by /{5}

This visually gives you:

Regular expression visualization

edited Jan 6, 2014 at 11:17

answered Jan 6, 2014 at 11:11

Stephan

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