feat(string): new template function

src/base.ts

@@ -1,5 +1,5 @@
 export const assert = (condition: boolean, message: string): asserts condition => {
   if (!condition) throw new Error(message)
 }
-export const toString = Object.prototype.toString
+export const toString = (v: any) => Object.prototype.toString.call(v)
 export const noop = () => {}

src/string.test.ts

@@ -0,0 +1,34 @@
+import { template } from './string'
+
+it('template', () => {
+  expect(
+    template(
+      'Hello {0}! My name is {1}.',
+      'Inès',
+      'Anthony',
+    ),
+  ).toEqual('Hello Inès! My name is Anthony.')
+
+  expect(
+    template(
+      '{0} + {1} = {2}{3}',
+      1,
+      '1',
+      { v: 2 },
+      [2, 3],
+    ),
+  ).toEqual('1 + 1 = [object Object]2,3')
+
+  expect(
+    template(
+      '{10}',
+    ),
+  ).toEqual('undefined')
+
+  expect(
+    template(
+      'Hi',
+      '',
+    ),
+  ).toEqual('Hi')
+})

src/string.ts

@@ -17,3 +17,24 @@ export function ensurePrefix(prefix: string, str: string) {
     return prefix + str
   return str
 }
+
+/**
+ * Dead simple template engine, just like Python's `.format()`
+ *
+ * @example
+ * ```
+ * const result = template(
+ *   'Hello {0}! My name is {1}.',
+ *   'Inès',
+ *   'Anthony'
+ * ) // Hello Inès! My name is Anthony.
+ * ```
+ */
+export function template(str: string, ...args: any[]): string {
+  return str.replace(/{(\d+)}/g, (match, key) => {
+    const index = Number(key)
+    if (Number.isNaN(index))
+      return match
+    return args[index]
+  })
+}