Do not copy Function#length (#23)

index.d.ts

@@ -1,6 +1,6 @@
 declare const mimicFn: {
 	/**
-	Make a function mimic another one. It will copy over the properties `name`, `length`, `displayName`, and any custom properties you may have set.
+	Make a function mimic another one. It will copy over the properties `name`, `displayName`, and any custom properties you may have set. The `length` property won't be copied.
 
 	@param to - Mimicking function.
 	@param from - Function to mimic.

index.js

@@ -1,7 +1,11 @@
 'use strict';
 
+const shouldCopyProperty = property => property !== 'length';
+
 const mimicFn = (to, from) => {
-	for (const prop of Reflect.ownKeys(from)) {
+	const props = Reflect.ownKeys(from).filter(shouldCopyProperty);
+
+	for (const prop of props) {
 		Object.defineProperty(to, prop, Object.getOwnPropertyDescriptor(from, prop));
 	}
 

readme.md

@@ -39,7 +39,7 @@ console.log(wrapper.unicorn);
 
 ## API
 
-It will copy over the properties `name`, `length`, `displayName`, and any custom properties you may have set.
+It will copy over the properties `name`, `displayName`, and any custom properties you may have set. The `length` property won't be copied.
 
 ### mimicFn(to, from)
 
@@ -61,7 +61,7 @@ Function to mimic.
 ## Related
 
 - [rename-fn](https://github.com/sindresorhus/rename-fn) - Rename a function
-- [keep-func-props](https://github.com/ehmicky/keep-func-props) - Wrap a function without changing its name, length and other properties
+- [keep-func-props](https://github.com/ehmicky/keep-func-props) - Wrap a function without changing its name and other properties
 
 
 ---

test.js

@@ -15,7 +15,7 @@ test('main', t => {
 	t.is(mimickFn(wrapper, foo), wrapper);
 
 	t.is(wrapper.name, 'foo');
-	t.is(wrapper.length, 1);
+	t.is(wrapper.length, 0);
 	t.is(wrapper.unicorn, '🦄');
 	t.is(wrapper[symbol], '✨');
 });