feat: withBase and withoutBase utils

src/utils.ts

@@ -7,26 +7,50 @@ export function hasProtocol (inputStr: string): boolean {
   return /^\w+:\/\//.test(inputStr)
 }
 
+export function hasTrailingSlash (input: string = ''): boolean {
+  return input.endsWith('/')
+}
+
 export function withoutTrailingSlash (input: string = ''): string {
-  return (input.endsWith('/') ? input.slice(0, -1) : input) || '/'
+  return (hasTrailingSlash(input) ? input.slice(0, -1) : input) || '/'
 }
 
 export function withTrailingSlash (input: string = ''): string {
   return input.endsWith('/') ? input : (input + '/')
 }
 
+export function hasLeadingSlash (input: string = ''): boolean {
+  return input.startsWith('/')
+}
+
 export function withoutLeadingSlash (input: string = ''): string {
-  return (input.startsWith('/') ? input.substr(1) : input) || '/'
+  return (hasLeadingSlash(input) ? input.substr(1) : input) || '/'
 }
 
 export function withLeadingSlash (input: string = ''): string {
-  return input.startsWith('/') ? input : ('/' + input)
+  return hasLeadingSlash(input) ? input : ('/' + input)
 }
 
 export function cleanDoubleSlashes (input: string = ''): string {
   return input.split('://').map(str => str.replace(/\/{2,}/g, '/')).join('://')
 }
 
+export function withBase (input: string, base: string) {
+  const _base = withoutTrailingSlash(base)
+  if (input.startsWith(_base)) {
+    return input
+  }
+  return joinURL(_base, input)
+}
+
+export function withoutBase (input: string, base: string) {
+  const _base = withoutTrailingSlash(base)
+  if (input.startsWith(_base)) {
+    return input.substr(_base.length) || '/'
+  }
+  return input
+}
+
 export function withQuery (input: string, query: QueryObject): string {
   const parsed = parseURL(input)
   const mergedQuery = { ...parseQuery(parsed.search), ...query }

test/base.test.ts

@@ -0,0 +1,41 @@
+// @ts-nocheck
+import { withBase, withoutBase } from '../src'
+
+describe('withBase', () => {
+  const tests = [
+    { base: '/', input: '/', out: '/' },
+    { base: '/foo', input: '/', out: '/foo' },
+    { base: '/foo/', input: '/', out: '/foo' },
+    { base: '/foo', input: '/bar', out: '/foo/bar' },
+    { base: '/base/', input: '/base', out: '/base' },
+    { base: '/base', input: '/base/', out: '/base/' },
+    { base: '/base', input: '/base/a', out: '/base/a' },
+    { base: '/base/', input: '/base/a', out: '/base/a' }
+  ]
+
+  for (const t of tests) {
+    test(JSON.stringify(t.base) + ' + ' + JSON.stringify(t.input), () => {
+      expect(withBase(t.input, t.base)).toBe(t.out)
+    })
+  }
+})
+
+describe('withoutBase', () => {
+  const tests = [
+    { base: '/', input: '/', out: '/' },
+    { base: '/foo', input: '/', out: '/' },
+    { base: '/foo/', input: '/', out: '/' },
+    { base: '/foo', input: '/bar', out: '/bar' },
+    { base: '/base/', input: '/base', out: '/' },
+    { base: '/base', input: '/base/', out: '/' },
+    { base: '/base', input: '/base/a', out: '/a' },
+    { base: '/base/', input: '/base/a', out: '/a' },
+    { base: '/base/a/', input: '/base/a', out: '/' }
+  ]
+
+  for (const t of tests) {
+    test(JSON.stringify(t.input) + '-' + JSON.stringify(t.base), () => {
+      expect(withoutBase(t.input, t.base)).toBe(t.out)
+    })
+  }
+})