memoize-one - npm Package Compare versions

Comparing version 2.0.1 to 3.0.0

lib/index.js

@@ -19,4 +19,3 @@ "use strict";
 
-  // breaking cache when context (this) or arguments change
-  return function () {
+  var result = function result() {
     for (var _len = arguments.length, newArgs = Array(_len), _key = 0; _key < _len; _key++) {
@@ -36,2 +35,4 @@ newArgs[_key] = arguments[_key];
   };
+
+  return result;
 };
@@ -38,0 +39,0 @@

package.json

 {
   "name": "memoize-one",
-  "version": "2.0.1",
+  "version": "3.0.0",
   "description": "A memoization library which only remembers the latest invocation",
@@ -24,3 +24,3 @@ "main": "lib/index.js",
     "eslint-plugin-flowtype": "2.32.1",
-    "flow-bin": "0.45.0",
+    "flow-bin": "0.46.0",
     "flow-copy-source": "1.1.0",
@@ -27,0 +27,0 @@ "mocha": "3.3.0",

src/index.js

 // @flow
-type EqualityFn = (a: any, b: any) => boolean;
+type EqualityFn = (a: mixed, b: mixed) => boolean;
 
-const simpleIsEqual = (a: any, b: any): boolean => a === b;
+const simpleIsEqual: EqualityFn = (a: mixed, b: mixed): boolean => a === b;
 
-export default function (resultFn: Function, isEqual?: EqualityFn = simpleIsEqual) {
-  let lastThis: any;
-  let lastArgs: Array<any> = [];
-  let lastResult: any;
+// <ResultFn: (...Array<any>) => mixed>
+// The purpose of this typing is to ensure that the returned memoized
+// function has the same type as the provided function (`resultFn`).
+// ResultFn:        Generic type (which is the same as the resultFn).
+// (...Array<any>): Accepts any length of arguments - and they are not checked
+// mixed:           The result can be anything but needs to be checked before usage
+export default function <ResultFn: (...Array<any>) => mixed>(resultFn: ResultFn, isEqual?: EqualityFn = simpleIsEqual): ResultFn {
+  let lastThis: mixed;
+  let lastArgs: Array<mixed> = [];
+  let lastResult: mixed;
   let calledOnce: boolean = false;
 
-  const isNewArgEqualToLast = (newArg, index) => isEqual(newArg, lastArgs[index]);
+  const isNewArgEqualToLast = (newArg: mixed, index: number): boolean => isEqual(newArg, lastArgs[index]);
 
-    // breaking cache when context (this) or arguments change
-  return function (...newArgs: Array<any>) {
+  // breaking cache when context (this) or arguments change
+  const result = function (...newArgs: Array<mixed>) {
     if (calledOnce &&
-            lastThis === this &&
-            newArgs.length === lastArgs.length &&
-            newArgs.every(isNewArgEqualToLast)) {
+      lastThis === this &&
+      newArgs.length === lastArgs.length &&
+      newArgs.every(isNewArgEqualToLast)) {
       return lastResult;
@@ -29,2 +35,5 @@ }
   };
-}
+
+  // telling flow to ignore the type of `result` as we know it is `ResultFn`
+  return (result: any);
+}

test/index.js

@@ -485,3 +485,21 @@ // @flow
   });
+
+  describe('flow typing', () => {
+    it('should maintain the type of the original function', () => {
+      // this test will create a flow error if the typing is incorrect
+      type SubtractFn = (a: number, b: number) => number;
+      const subtract: SubtractFn = (a: number, b: number): number => a - b;
+      const requiresASubtractFn = (fn: SubtractFn): number => fn(2, 1);
+
+      const memoizedSubtract: SubtractFn = memoizeOne(subtract);
+
+      // will cause a flow error if `fn` is not of type `SubtractFn`
+      const result1 = requiresASubtractFn(memoizedSubtract);
+      const result2 = requiresASubtractFn(memoizeOne(subtract));
+
+      expect(result1).to.equal(1);
+      expect(result2).to.equal(1);
+    });
+  });
 });
 

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Improved metrics

Total package byte prevSize

138772

increased by1.52%

Lines of code

483

increased by4.55%

No dependency changes