@autobind decorator.

src/decorators.js

@@ -1,3 +1,57 @@
+import bind from 'lodash.bind'
+
+// ===================================================================
+
+const {defineProperty} = Object
+
+// ===================================================================
+
+// See: https://github.com/jayphelps/core-decorators.js#autobind
+export function autobind (target, key, {
+  configurable,
+  enumerable,
+  value: fn,
+  writable
+}) {
+  return {
+    configurable,
+    enumerable,
+
+    get () {
+      const bounded = bind(fn, this)
+
+      defineProperty(this, key, {
+        configurable: true,
+        enumerable: false,
+        value: bounded,
+        writable: true
+      })
+
+      return bounded
+    },
+    set (newValue) {
+      if (this === target) {
+        // New value directly set on the prototype.
+        delete this[key]
+        this[key] = newValue
+      } else {
+        // New value set on a child object.
+
+        // Cannot use assignment because it will call the setter on
+        // the prototype.
+        defineProperty(this, key, {
+          configurable: true,
+          enumerable: true,
+          value: newValue,
+          writable: true
+        })
+      }
+    }
+  }
+}
+
+// -------------------------------------------------------------------
+
 // Debounce decorator for methods.
 //
 // See: https://github.com/wycats/javascript-decorators

src/decorators.spec.js

@@ -0,0 +1,72 @@
+/* eslint-env mocha */
+
+import {expect} from 'chai'
+
+// ===================================================================
+
+import {autobind, debounce} from './decorators'
+
+// ===================================================================
+
+describe('autobind', function () {
+  class Foo {
+    @autobind
+    getFoo () {
+      return this
+    }
+  }
+
+  it('returns a bound instance for a method', function () {
+    const foo = new Foo()
+    const {getFoo} = foo
+
+    expect(getFoo()).to.equal(foo)
+  })
+
+  it('works with multiple instances of the same class', function () {
+    const foo1 = new Foo()
+    const foo2 = new Foo()
+
+    const {getFoo: getFoo1} = foo1
+    const {getFoo: getFoo2} = foo2
+
+    expect(getFoo1()).to.equal(foo1)
+    expect(getFoo2()).to.equal(foo2)
+  })
+})
+
+// -------------------------------------------------------------------
+
+describe('debounce', function () {
+  let i
+
+  class Foo {
+    @debounce(1e1)
+    foo () {
+      ++i
+    }
+  }
+
+  beforeEach(function () {
+    i = 0
+  })
+
+  it('works', function (done) {
+    const foo = new Foo()
+
+    expect(i).to.equal(0)
+
+    foo.foo()
+    expect(i).to.equal(1)
+
+    foo.foo()
+    expect(i).to.equal(1)
+
+    setTimeout(function () {
+      foo.foo()
+      expect(i).to.equal(2)
+
+      done()
+    }, 2e1)
+  })
+})