refactor: simplify html parser regex

Author: yyx990803

src/compiler/parser/html-parser.js

@@ -13,29 +13,14 @@ import { makeMap, no } from 'shared/util'
 import { isNonPhrasingTag } from 'web/compiler/util'
 
 // Regular Expressions for parsing tags and attributes
-const singleAttrIdentifier = /([^\s"'<>/=]+)/
-const singleAttrAssign = /(=)/
-const singleAttrValues = [
-  // attr value double quotes
-  /"([^"]*)"+/.source,
-  // attr value, single quotes
-  /'([^']*)'+/.source,
-  // attr value, no quotes
-  /([^\s"'=<>`]+)/.source
-]
-const attribute = new RegExp(
-  '^\\s*' + singleAttrIdentifier.source +
-  '(?:\\s*' + singleAttrAssign.source +
-  '\\s*(?:' + singleAttrValues.join('|') + '))?'
-)
-
+const attribute = /^\s*([^\s"'<>\/=]+)(?:\s*(=)\s*(?:"([^"]*)"+|'([^']*)'+|([^\s"'=<>`]+)))?/
 // could use https://www.w3.org/TR/1999/REC-xml-names-19990114/#NT-QName
 // but for Vue templates we can enforce a simple charset
 const ncname = '[a-zA-Z_][\\w\\-\\.]*'
-const qnameCapture = '((?:' + ncname + '\\:)?' + ncname + ')'
-const startTagOpen = new RegExp('^<' + qnameCapture)
+const qnameCapture = `((?:${ncname}\\:)?${ncname})`
+const startTagOpen = new RegExp(`^<${qnameCapture}`)
 const startTagClose = /^\s*(\/?)>/
-const endTag = new RegExp('^<\\/' + qnameCapture + '[^>]*>')
+const endTag = new RegExp(`^<\\/${qnameCapture}[^>]*>`)
 const doctype = /^<!DOCTYPE [^>]+>/i
 const comment = /^<!--/
 const conditionalComment = /^<!\[/