memoize-one - npm Package Compare versions

Comparing version 1.0.0-rc.1 to 1.0.0

lib/index.js

@@ -10,2 +10,3 @@ "use strict";
 
+    var lastThis = void 0;
     var lastArgs = [];
@@ -15,2 +16,3 @@ var lastResult = void 0;
 
+    // breaking cache when arguments or context changes
     return function () {
@@ -21,3 +23,3 @@ for (var _len = arguments.length, newArgs = Array(_len), _key = 0; _key < _len; _key++) {
 
-        if (calledOnce && newArgs.length === lastArgs.length && lastArgs.every(function (lastArg, i) {
+        if (calledOnce && lastThis === this && newArgs.length === lastArgs.length && lastArgs.every(function (lastArg, i) {
             return isEqual(lastArg, newArgs[i]);
@@ -29,2 +31,3 @@ })) {
         calledOnce = true;
+        lastThis = this;
         lastArgs = newArgs;
@@ -31,0 +34,0 @@ lastResult = resultFn.apply(this, newArgs);

package.json

 {
   "name": "memoize-one",
-  "version": "1.0.0-rc.1",
-  "description": "A memoization library for memoizing a function with a cache size of one",
+  "version": "1.0.0",
+  "description": "A memoization library which only remembers the latest invokation",
   "main": "lib/index.js",
@@ -47,3 +47,8 @@ "module": "src/index.js",
     "prepublish": "yarn run build"
-  }
+  },
+  "keywords": [
+    "memoize",
+    "cache",
+    "performance"
+  ]
 }

README.md

 # memoizeOne
 
-A simple memoization library which only remembers the latest invokation
+A memoization library which only remembers the latest invokation
 
-[![Build Status](https://travis-ci.org/alexreardon/memoize-one.svg?branch=master)](https://travis-ci.org/alexreardon/memoize-one)
-[![codecov](https://codecov.io/gh/alexreardon/memoize-one/branch/master/graph/badge.svg)](https://codecov.io/gh/alexreardon/memoize-one)
+[![Build Status](https://travis-ci.org/alexreardon/memoize-one.svg?branch=master)](https://travis-ci.org/alexreardon/memoize-one) [![codecov](https://codecov.io/gh/alexreardon/memoize-one/branch/master/graph/badge.svg)](https://codecov.io/gh/alexreardon/memoize-one) [![dependencies](https://david-dm.org/alexreardon/memoize-one.svg)](https://david-dm.org/alexreardon/memoize-one) [![SemVer](https://img.shields.io/badge/SemVer-2.0.0-brightgreen.svg)](http://semver.org/spec/v2.0.0.html)
 
-## DOCS: Work in progress
-
 ## Rationale
@@ -20,5 +17,4 @@
 
-Unlike other memoization libraries, `memoizeOne` only remembers the latest arguments. No need to worry about cache busting mechanisms such as `maxAge`, `maxSize`, `exlusions` and so on which can be prone to memory leaks. `memoizeOne` simply remembers the last arguments, and if the function is next called with the same arguments then it returns the previous result.
+Unlike other memoization libraries, `memoizeOne` only remembers the latest arguments and result. No need to worry about cache busting mechanisms such as `maxAge`, `maxSize`, `exlusions` and so on which can be prone to memory leaks. `memoizeOne` simply remembers the last arguments, and if the function is next called with the same arguments then it returns the previous result.
 
-
 ## Usage
@@ -50,2 +46,3 @@
 ```
+[Play with this example](http://www.webpackbin.com/NkCiYkz_M)
 
@@ -74,3 +71,11 @@ ### Custom equality function
 ```
+[Play with this example](http://www.webpackbin.com/NJW-tJMdf)
 
+#### Type signature
+Here is the expected [flow](http://flowtype.org) type signature for a custom equality function:
+
+```js
+type EqualityFn = (a: any, b: any) => boolean;
+```
+
 ## Installation
@@ -86,13 +91,46 @@
 
-## Other features
+## `this`
 
-### Correctly supports `this` binding
+### memoizeOne correctly respects `this` control
 
-### Custom equality function
+This library takes special care to maintain, and allow control over the the `this` context for **both** the original function being memoized as well as the returned memoized function. Both the original function and the memoized function's `this` context respect [all the `this` controlling techniques](https://github.com/getify/You-Dont-Know-JS/blob/master/this%20%26%20object%20prototypes/ch2.md):
 
-### Code health
+- new bindings (`new`)
+- explicit binding (`call`, `apply`, `bind`);
+- implicit binding (call site: `obj.foo()`);
+- default binding (`window` or `undefined` in `strict mode`);
+- fat arrow binding (binding to lexical `this`)
+- ignored this (pass `null` as `this` to explicit binding)
 
-- Tested with [all JavaScript *types*](https://github.com/getify/You-Dont-Know-JS/blob/master/types%20%26%20grammar/ch1.md)
-- 100% code coverage
-- [flow types](http://flowtype.org) for safer internal execution and type checking / auto complete for editors
-- [Semantically versioning (2.0)](http://semver.org/)
+### Changes to `this` is considered an argument change
+
+Changes to the running context (`this`) of a function can result in the function returning a different value event though its arguments have stayed the same:
+
+```js
+function getA() {
+    return this.a;
+}
+
+const temp1 = {
+    a: 20,
+};
+const temp2 = {
+    a: 30,
+}
+
+getA.call(temp1); // 20
+getA.call(temp2); // 30
+```
+
+Therefore, in order to prevent against unexpected results, `memoizeOne` takes into account the current execution context (`this`) of the memoized function. If `this` is different to the previous invokation then it is considered a change in argument. [further discussion](https://github.com/alexreardon/memoize-one/issues/3).
+
+Generally this will be of no impact if you are not explicity controlling the `this` context of functions you want to memoize with [explicit binding](https://github.com/getify/You-Dont-Know-JS/blob/master/this%20%26%20object%20prototypes/ch2.md#explicit-binding)  or [implicit binding](https://github.com/getify/You-Dont-Know-JS/blob/master/this%20%26%20object%20prototypes/ch2.md#implicit-binding). `memoizeOne` will detect when you are manipulating `this` and will then consider the `this` context as an argument. If `this` changes, it will re-execute the original function even if the arguments have not changed.
+
+
+## Code health
+
+- Tested with all built in [JavaScript types](https://github.com/getify/You-Dont-Know-JS/blob/master/types%20%26%20grammar/ch1.md).
+- 100% code coverage.
+- [flow types](http://flowtype.org) for safer internal execution and external consumption. Also allows for editor autocompletion.
+- Follows [Semantic versioning (2.0)](http://semver.org/) for safer versioning.
+- Lightweight with no dependencies

src/index.js

@@ -7,2 +7,3 @@ // @flow
 export default function (resultFn: Function, isEqual?: EqualityFn = simpleIsEqual) {
+    let lastThis: any;
     let lastArgs: Array<any> = [];
@@ -12,4 +13,7 @@ let lastResult: any;
 
+    // breaking cache when arguments or context changes
     return function (...newArgs: Array<any>) {
-        if (calledOnce && newArgs.length === lastArgs.length &&
+        if (calledOnce &&
+            lastThis === this &&
+            newArgs.length === lastArgs.length &&
             lastArgs.every((lastArg, i) => isEqual(lastArg, newArgs[i]))) {
@@ -20,2 +24,3 @@ return lastResult;
         calledOnce = true;
+        lastThis = this;
         lastArgs = newArgs;
@@ -22,0 +27,0 @@ lastResult = resultFn.apply(this, newArgs);

test/index.js

@@ -7,24 +7,69 @@ // @flow
 
-type Expectation = {|
-    args: any[],
-    result: any
-|};
+describe('memoizeOne', () => {
+    function getA() {
+        // $FlowSuppressError: allowing many values for `this`
+        return this.a;
+    }
 
-type Input = {|
-    name: string,
-    first: Expectation,
-    second: Expectation
-|};
+    describe('standard behaviour - baseline', () => {
+        let add;
+        let memoizedAdd;
 
-describe('memoizeOne', () => {
-    // [JavaScript defines seven built-in types:](https://github.com/getify/You-Dont-Know-JS/blob/master/types%20%26%20grammar/ch1.md)
-    //    - null
-    //    - undefined
-    //    - boolean
-    //    - number
-    //    - string
-    //    - object
-    //    - symbol
+        beforeEach(() => {
+            add = sinon.spy((value1: number, value2: number): number => value1 + value2);
+            memoizedAdd = memoizeOne(add);
+        });
 
-    describe('standard behaviour', () => {
+        it('should return the result of a function', () => {
+            expect(memoizedAdd(1, 2)).to.equal(3);
+        });
+
+        it('should return the same result if the arguments have not changed', () => {
+            expect(memoizedAdd(1, 2)).to.equal(3);
+            expect(memoizedAdd(1, 2)).to.equal(3);
+        });
+
+        it('should not execute the memoized function if the arguments have not changed', () => {
+            memoizedAdd(1, 2);
+            memoizedAdd(1, 2);
+
+            expect(add.callCount).to.equal(1);
+        });
+
+        it('should invalidate a memoize cache if new arguments are provided', () => {
+            expect(memoizedAdd(1, 2)).to.equal(3);
+            expect(memoizedAdd(2, 2)).to.equal(4);
+            expect(add.callCount).to.equal(2);
+        });
+
+        it('should resume memoization after a cache invalidation', () => {
+            expect(memoizedAdd(1, 2)).to.equal(3);
+            expect(add.callCount).to.equal(1);
+            expect(memoizedAdd(2, 2)).to.equal(4);
+            expect(add.callCount).to.equal(2);
+            expect(memoizedAdd(2, 2)).to.equal(4);
+            expect(add.callCount).to.equal(2);
+        });
+    });
+
+    describe('standard behaviour - dynamic', () => {
+        type Expectation = {|
+            args: any[],
+            result: any
+        |};
+
+        type Input = {|
+            name: string,
+            first: Expectation,
+            second: Expectation
+        |};
+
+        // [JavaScript defines seven built-in types:](https://github.com/getify/You-Dont-Know-JS/blob/master/types%20%26%20grammar/ch1.md)
+        //    - null
+        //    - undefined
+        //    - boolean
+        //    - number
+        //    - string
+        //    - object
+        //    - symbol
         const inputs: Input[] = [
@@ -132,3 +177,3 @@ {
         inputs.forEach(({ name, first, second }) => {
-            describe(`dynamic type test:[${name}]`, () => {
+            describe(`type: [${name}]`, () => {
 
@@ -189,6 +234,16 @@ let spy;
         describe('original function', () => {
-            function getA() {
-                return this.a;
-            }
+            it('should respect new bindings', () => {
+                const Foo = function (bar) {
+                    this.bar = bar;
+                };
+                const memoized = memoizeOne(function (bar) {
+                    return new Foo(bar);
+                });
 
+                const result = memoized('baz');
+
+                expect(result instanceof Foo).to.equal(true);
+                expect(result.bar).to.equal('baz');
+            });
+
             it('should respect explicit bindings', () => {
@@ -216,5 +271,36 @@ const temp = {
 
-            it('should respect default bindings', () => {
-                const memoized = memoizeOne(getA);
+            it('should respect implicit bindings', () => {
+                const temp = {
+                    a: 2,
+                    getA,
+                };
 
+                const memoized = memoizeOne(function () {
+                    return temp.getA();
+                });
+
+                expect(memoized()).to.equal(2);
+            });
+
+            it('should respect fat arrow bindings', () => {
+                const temp = {
+                    a: 50,
+                };
+                function foo() {
+                    // return an arrow function
+                    return () => {
+                        // `this` here is lexically adopted from `foo()`
+                        return getA.call(this);
+                    };
+                }
+                const bound = foo.call(temp);
+                const memoized = memoizeOne(bound);
+
+                expect(memoized()).to.equal(50);
+            });
+
+            it('should respect ignored bindings', () => {
+                const bound = getA.bind(null);
+                const memoized = memoizeOne(bound);
+
                 expect(memoized).to.throw(TypeError);
@@ -225,6 +311,16 @@ });
         describe('memoized function', () => {
-            function getA() {
-                return this.a;
-            }
+            it('should respect new bindings', () => {
+                const memoizedGetA = memoizeOne(getA);
+                const Foo = function (a) {
+                    this.a = a;
+                    this.result = memoizedGetA.call(this);
+                };
 
+                const foo1 = new Foo(10);
+                const foo2 = new Foo(20);
+
+                expect(foo1.result).to.equal(10);
+                expect(foo2.result).to.equal(20);
+            });
+
             it('should respect implicit bindings', () => {
@@ -272,5 +368,60 @@ const getAMemoized = memoizeOne(getA);
             });
+
+            it('should respect implicit bindings', () => {
+                const getAMemoized = memoizeOne(getA);
+                const temp = {
+                    a: 2,
+                    getAMemoized,
+                };
+
+                expect(temp.getAMemoized()).to.equal(2);
+            });
+
+            it('should respect fat arrow bindings', () => {
+                const temp = {
+                    a: 50,
+                };
+                const memoizedGetA = memoizeOne(getA);
+                function foo() {
+                    // return an arrow function
+                    return () => {
+                        // `this` here is lexically adopted from `foo()`
+                        return memoizedGetA.call(this);
+                    };
+                }
+                const bound = foo.call(temp);
+                const memoized = memoizeOne(bound);
+
+                expect(memoized()).to.equal(50);
+            });
+
+            it('should respect ignored bindings', () => {
+                const memoized = memoizeOne(getA);
+
+                const getResult = function () {
+                    return memoized.call(null);
+                };
+
+                expect(getResult).to.throw(TypeError);
+            });
         });
     });
 
+    describe('context change', () => {
+        it('should break the memoization cache if the execution context changes', () => {
+            const memoized = memoizeOne(getA);
+            const temp1 = {
+                a: 20,
+                getMemoizedA: memoized,
+            };
+            const temp2 = {
+                a: 30,
+                getMemoizedA: memoized,
+            };
+
+            expect(temp1.getMemoizedA()).to.equal(20);
+            expect(temp2.getMemoizedA()).to.equal(30);
+        });
+    });
+
     describe('custom equality function', () => {
@@ -338,44 +489,3 @@ let add;
     });
-
-    describe('standard behaviour', () => {
-        let add;
-        let memoizedAdd;
-
-        beforeEach(() => {
-            add = sinon.spy((value1: number, value2: number): number => value1 + value2);
-            memoizedAdd = memoizeOne(add);
-        });
-
-        it('should return the result of a function', () => {
-            expect(memoizedAdd(1, 2)).to.equal(3);
-        });
-
-        it('should return the same result if the arguments have not changed', () => {
-            expect(memoizedAdd(1, 2)).to.equal(3);
-            expect(memoizedAdd(1, 2)).to.equal(3);
-        });
-
-        it('should not execute the memoized function if the arguments have not changed', () => {
-            memoizedAdd(1, 2);
-            memoizedAdd(1, 2);
-
-            expect(add.callCount).to.equal(1);
-        });
-
-        it('should invalidate a memoize cache if new arguments are provided', () => {
-            expect(memoizedAdd(1, 2)).to.equal(3);
-            expect(memoizedAdd(2, 2)).to.equal(4);
-            expect(add.callCount).to.equal(2);
-        });
-
-        it('should resume memoization after a cache invalidation', () => {
-            expect(memoizedAdd(1, 2)).to.equal(3);
-            expect(add.callCount).to.equal(1);
-            expect(memoizedAdd(2, 2)).to.equal(4);
-            expect(add.callCount).to.equal(2);
-            expect(memoizedAdd(2, 2)).to.equal(4);
-            expect(add.callCount).to.equal(2);
-        });
-    });
 });
 

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