Added "is" and "isinstance"

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "typescript.tsdk": "node_modules/typescript/lib"
+}

README.md

@@ -82,6 +82,23 @@ bool({x: 1});  // => true
 a === identity(a)  // => true
 ```
 
+**is** and **isinstance** checks for strict equality and inheritance:
+
+```typescript
+const f = is(8);
+f(8)      // => true
+f(5 + 3)  // => true
+f("8")    // => false
+f(null)   // => false
+
+class A { }
+class A1 extends A { }
+class A2 extends A { }
+class B { }
+const f: any[] = [5, null, undefined, new A, new A1, new B, new A2];
+const result: A[] = f.filter(isinstance(A));  // => [f[3], f[4], f[6]]
+```
+
 **nn**, **nu** and **nnu** checks at run-time for null or undefined:
 
 ```typescript

package.json

@@ -1,6 +1,6 @@
 {
   "name": "tk-functional",
-  "version": "0.1.5",
+  "version": "0.2.0",
   "description": "Typescript/Javascript helpers for functional-style programming",
   "source": "src/index.ts",
   "main": "dist/tk-functional.umd.js",
@@ -18,7 +18,8 @@
     "prepublishOnly": "npm test",
     "dev": "run-p dev:*",
     "dev:test": "jest --watchAll",
-    "dev:build": "microbundle watch -f modern,umd"
+    "dev:build": "microbundle watch -f modern,umd",
+    "dev:serve": "live-server --host=localhost --port=5000 --no-browser dist"
   },
   "author": {
     "name": "Michaël Lemaire",
@@ -37,7 +38,7 @@
     "typescript"
   ],
   "devDependencies": {
-    "tk-base": "^0.2.1"
+    "tk-base": "^0.2.3"
   },
   "dependencies": {}
-}
+}

src/index.test.ts

@@ -1,4 +1,4 @@
-import { always, and, attr, bool, cmp, fmap, identity, never, nn, nnu, nop, nu, or, partial, pipe } from "./index";
+import { always, and, attr, bool, cmp, fmap, identity, is, isinstance, never, nn, nnu, nop, nu, or, partial, pipe } from "./index";
 
 describe(nop, () => {
   it("does nothing", () => {
@@ -74,6 +74,38 @@ describe(or, () => {
   });
 });
 
+describe(is, () => {
+  it("checks for equality", () => {
+    const f = is(5);
+    expect(f(5)).toBe(true);
+    expect(f(4)).toBe(false);
+    expect(f("a" as any)).toBe(false);
+    expect(f(null as any)).toBe(false);
+    expect(f(undefined as any)).toBe(false);
+  });
+
+  it("applies strict equality", () => {
+    const obj: { x: number } = { x: 1 };
+    let f = is(obj);
+    expect(f(obj)).toBe(true);
+    expect(f({ x: 1 })).toBe(false);
+    expect(f({ y: 1 } as any)).toBe(false);
+  });
+});
+
+describe(isinstance, () => {
+  it("checks for subclasses", () => {
+    class A { }
+    class A1 extends A { }
+    class A2 extends A { }
+    class B { }
+
+    const f: any[] = [5, null, undefined, new A, new A1, new B, new A2];
+    const result = f.filter(isinstance(A));
+    expect(result).toEqual([f[3], f[4], f[6]]);
+  });
+});
+
 describe(pipe, () => {
   it("pipes two functions", () => {
     const f = pipe((x: number) => x * 2, (x: number) => x + 1);

src/index.ts

@@ -77,6 +77,20 @@ export function or<A extends any[]>(...predicates: ((...args: A) => boolean)[]):
   }
 }
 
+/**
+ * Get a function to check the strict equality with a reference
+ */
+export function is<T, S extends T>(ref: T): (input: S) => input is Extract<T, S> {
+  return (x): x is Extract<T, S> => x === ref;
+}
+
+/**
+ * Get a function to check that inputs are instances of a given type
+ */
+export function isinstance<T, S extends T>(ref: { new(...args: any[]): T }): (input: S) => input is Extract<T, S> {
+  return (x): x is Extract<T, S> => x instanceof ref;
+}
+
 /**
  * Pipe the result of a function as first parameter of another, to create a new function
  */

tsconfig.json

@@ -12,5 +12,10 @@
       "dom",
       "es6"
     ]
-  }
+  },
+  "exclude": [
+    "node_modules",
+    "dist",
+    "src/**/*.test.ts"
+  ]
 }