feat: add isRelative helper (#17)

README.md

@@ -123,6 +123,15 @@ Check two paths are equal or not. Trailing slash and encoding are normalized bef
 isSamePath('/foo', '/foo/')
 ```
 
+### `isRelative`
+
+Check if a path starts with `./` or `../`.
+
+```ts
+// Result: true
+isRelative('./foo')
+```
+
 ## License
 
 [MIT](./LICENSE)

src/utils.ts

@@ -3,6 +3,10 @@ import { parseURL, stringifyParsedURL } from './parse'
 import { QueryObject, parseQuery, stringifyQuery } from './query'
 import { decode } from './encoding'
 
+export function isRelative (inputStr: string) {
+  return ['./', '../'].some(str => inputStr.startsWith(str))
+}
+
 export function hasProtocol (inputStr: string, acceptProtocolRelative = false): boolean {
   return /^\w+:\/\/.+/.test(inputStr) || (acceptProtocolRelative && /^\/\/[^/]+/.test(inputStr))
 }

test/utilities.test.ts

@@ -1,4 +1,4 @@
-import { hasProtocol } from '../src'
+import { hasProtocol, isRelative } from '../src'
 
 describe('hasProtocol', () => {
   const tests = [
@@ -19,3 +19,18 @@ describe('hasProtocol', () => {
     })
   }
 })
+
+describe('isRelative', () => {
+  const tests = [
+    { input: '/', out: false },
+    { input: './/', out: true },
+    { input: '../test', out: true },
+    { input: 'https://', out: false }
+  ]
+
+  for (const t of tests) {
+    test(t.input.toString(), () => {
+      expect(isRelative(t.input)).toBe(t.out)
+    })
+  }
+})