perf(helper/cookie): fast-path for name specified

src/utils/cookie.test.ts

@@ -30,6 +30,14 @@ describe('Parse cookie', () => {
     expect(cookie['tasty_cookie']).toBeUndefined()
   })
 
+  it('Should parse one cookie specified by name even if it is not found', () => {
+    const cookieString = 'yummy_cookie=choco; tasty_cookie = strawberry '
+    const cookie: Cookie = parse(cookieString, 'no_such_cookie')
+    expect(cookie['yummy_cookie']).toBeUndefined()
+    expect(cookie['tasty_cookie']).toBeUndefined()
+    expect(cookie['no_such_cookie']).toBeUndefined()
+  })
+
   it('Should parse cookies with no value', () => {
     const cookieString = 'yummy_cookie=; tasty_cookie = ; best_cookie= ; last_cookie=""'
     const cookie: Cookie = parse(cookieString)

src/utils/cookie.ts

@@ -77,17 +77,22 @@ const validCookieNameRegEx = /^[\w!#$%&'*.^`|~+-]+$/
 const validCookieValueRegEx = /^[ !#-:<-[\]-~]*$/
 
 export const parse = (cookie: string, name?: string): Cookie => {
+  if (name && cookie.indexOf(name) === -1) {
+    // Fast-path: return immediately if the demanded-key is not in the cookie string
+    return {}
+  }
   const pairs = cookie.trim().split(';')
-  return pairs.reduce((parsedCookie, pairStr) => {
+  const parsedCookie: Cookie = {}
+  for (let pairStr of pairs) {
     pairStr = pairStr.trim()
     const valueStartPos = pairStr.indexOf('=')
     if (valueStartPos === -1) {
-      return parsedCookie
+      continue
     }
 
     const cookieName = pairStr.substring(0, valueStartPos).trim()
     if ((name && name !== cookieName) || !validCookieNameRegEx.test(cookieName)) {
-      return parsedCookie
+      continue
     }
 
     let cookieValue = pairStr.substring(valueStartPos + 1).trim()
@@ -96,10 +101,13 @@ export const parse = (cookie: string, name?: string): Cookie => {
     }
     if (validCookieValueRegEx.test(cookieValue)) {
       parsedCookie[cookieName] = decodeURIComponent_(cookieValue)
+      if (name) {
+        // Fast-path: return only the demanded-key immediately. Other keys are not needed.
+        break
+      }
     }
-
-    return parsedCookie
-  }, {} as Cookie)
+  }
+  return parsedCookie
 }
 
 export const parseSigned = async (