JS正则表达式根据不带反斜杠的字符拆分字符串

Question

I want to use the JS String split function to split this string based only on the commas , , and not the commas preceded by backslashes /, . How can I do this?

'this,is\,a,\,string'.split(/,/)

This code splits it on all strings, I'm not sure how to get it to split just on the commas not preceded by backslashes.

Answer 1

Since lookbehinds are not supported in JavaScript, it's hard to define "not preceded by something" pattern for split. However, you may define a "word" as a sequence of non-commas or escaped commas:

(?:\\,|[^,])+

(demo: https://regex101.com/r/d5W21v/1)

and extract all "word" matches:

 var matches = "this,is\\\\,a,\\\\,string".match(/(?:\\\\,|[^,])+/g); console.log(matches); 

Answer 2

Replace the non-splitting symbol with a temporary symbol, split, and then restore the non-splitting symbol

 'this,is\,a,\,string'.replace('\,','##NONBREAKING##').split(',')

Then loop over the resulting array, replacing '##NONBREAKING##' with '\\,'.

Obviously the temporary symbol '##NONBREAKING##' must be something that can never occur in the text you are breaking. Perhaps include some Unicode characters that are hard to type in? Or include characters from multiple different languages (eg chinese, russian, indian, native american) that are unlikely to appear together in genuine text.

Answer 3

I think what you're looking for is called " Negative Lookbehind " - a regex element that looks back in the string and makes sure the pattern is not preceded by another pattern.

However, Javascript doesn't natively support Lookbehind. It does, however, (Negative and positive) Support Lookahead.

So you could: 1. reverse the string 2. split by comma (unless it's followed by slash) 3. reverse the words back 4. reverse order of words

var temp = "this,is\\,a,\\,string"
var reversed = temp.split('').reverse().join('')
var words = t2.split(/,(?!\\)/).map(x => x.split('').reverse().join(''))
var finalResult = words.reverse()

It's kindof cumbersome though...

Answer 4

You can create alternatively a custom method which retrieves an array. If a comma found and its not preceded by a backslash, substring. Obviously you need a counter to update the position next to the comma.

Hope this can be helpful

Answer 5

This method is only currently supported in Chrome 62 (desktop and Android), Opera 49, and Node.js 8.10

A limited set of JavaScript engines now support lookbehinds, so the following works in supported environments:

 console.log('this,is\\\\,a,\\\\,string'.split(/(?<!\\\\),/)) 

Since this doesn't currently work in Firefox, Safari, or iOS Chrome (among others), it's not particularly useful for client-side development, but it is useful for Node apps.

Mozilla has an up-to-date browser compatibility section for regex lookbehinds.