Bind

README.md

@@ -35,6 +35,13 @@ var count = normalize('number', function(a, b) {
 }, 1, 2);
 // count === 3
 
+// Bind the function to supply it with context
+var context = { c: 3 };
+var count = normalize.bind(context)('number', function(a, b) {
+  return a + b + this.c;
+}, 1, 2);
+// count === 6
+
 // Values one of multiple types are returned
 var isEnabled = normalize(['string', 'boolean'], true);
 // isEnabled === true

index.js

@@ -18,13 +18,13 @@ function normalize(coercer, value) {
     if (coercer === 'function') {
       return value;
     }
-    value = value.apply(null, Array.prototype.slice.call(arguments, 2));
+    value = value.apply(this, Array.prototype.slice.call(arguments, 2));
   }
-  return coerce(coercer, value);
+  return coerce(this, coercer, value);
 }
 
 
-function coerce(coercer, value) {
+function coerce(context, coercer, value) {
 
   // Handle built-in types
   if (typeof coercer === 'string') {
@@ -36,13 +36,13 @@ function coerce(coercer, value) {
 
   // Handle custom coercer
   if (typeof coercer === 'function') {
-    return coercer(value);
+    return coercer.call(context, value);
   }
 
   // Array of coercers, try in order until one returns a non-null value
   var result = null;
   coercer.some(function(coercer) {
-    result = coerce(coercer, value);
+    result = coerce(context, coercer, value);
     return result !== null;
   });
 
@@ -99,10 +99,17 @@ function primitive(value) {
 }
 
 
-// Add methods for each type
-types.forEach(function(type) {
-  normalize[type] = normalize.bind(null, type);
-});
+function bind(context) {
+  var fun = Function.prototype.bind.call(normalize, context);
+  fun.bind = bind;
+
+  // Add methods for each type
+  types.forEach(function(type) {
+    fun[type] = Function.prototype.bind.call(normalize, context, type);
+  });
+
+  return fun;
+}
 
 
-module.exports = normalize;
+module.exports = bind(null);

test/index.js

@@ -46,17 +46,17 @@ describe('normalize', function() {
     done();
   });
 
-  it('supports functions for the type parameter', function(done) {
+  it('supports coercer functions for the type parameter', function(done) {
     var type = function() {
       return true;
     };
     var value = 1;
     var result = normalize(type, value);
-    expect(result).toEqual(value);
+    expect(result).toBe(true);
     done();
   });
 
-  it('calls the type function to attempt coercion', function(done) {
+  it('calls the coercer function to attempt coercion', function(done) {
     var expected = 1;
     var type = expect.createSpy().andCall(function(value) {
       return value;
@@ -67,6 +67,19 @@ describe('normalize', function() {
     done();
   });
 
+  it('calls the coercer functions with context, if bound', function(done) {
+    var expected = 1;
+    var context = {};
+    var type = expect.createSpy().andCall(function(value) {
+      expect(this).toBe(context);
+      return value;
+    });
+    var result = normalize.bind(context)(type, expected);
+    expect(result).toEqual(expected);
+    expect(type).toHaveBeenCalled();
+    done();
+  });
+
   it('calls the value if it is a function', function(done) {
     var type = 'string';
     var expected = 'test string';
@@ -79,6 +92,17 @@ describe('normalize', function() {
     done();
   });
 
+  it('calls the value function with context, if bound', function(done) {
+    var type = 'string';
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context)(type, value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
+
   it('checks the result of function against coercer', function(done) {
     var expected = 'test string';
     var coercer = expect.createSpy().andCall(function(value) {
@@ -163,6 +187,16 @@ describe('normalize.object', function() {
     expect(result).toEqual(null);
     done();
   });
+
+  it('calls the object function with context, if bound', function(done) {
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context).object(value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
 });
 
 describe('normalize.number', function() {
@@ -202,6 +236,16 @@ describe('normalize.number', function() {
     expect(result).toEqual(null);
     done();
   });
+
+  it('calls the number function with context, if bound', function(done) {
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context).number(value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
 });
 
 describe('normalize.string', function() {
@@ -250,6 +294,16 @@ describe('normalize.string', function() {
     expect(result).toEqual(null);
     done();
   });
+
+  it('calls the string function with context, if bound', function(done) {
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context).string(value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
 });
 
 describe('normalize.symbol', function() {
@@ -278,6 +332,21 @@ describe('normalize.symbol', function() {
     expect(result).toEqual(null);
     done();
   });
+
+  it('calls the symbol function with context, if bound', function(done) {
+    if (!global.Symbol) {
+      console.log('Only available on platforms that support Symbol');
+      this.skip();
+      return;
+    }
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context).symbol(value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
 });
 
 describe('normalize.boolean', function() {
@@ -303,6 +372,16 @@ describe('normalize.boolean', function() {
     expect(result).toEqual(null);
     done();
   });
+
+  it('calls the boolean function with context, if bound', function(done) {
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context).boolean(value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
 });
 
 describe('normalize.function', function() {
@@ -345,6 +424,16 @@ describe('normalize.undefined', function() {
     expect(result).toEqual(null);
     done();
   });
+
+  it('calls the undefined function with context, if bound', function(done) {
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context).undefined(value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
 });
 
 describe('normalize.date', function() {
@@ -413,4 +502,14 @@ describe('normalize.date', function() {
     expect(result).toEqual(null);
     done();
   });
+
+  it('calls the date function with context, if bound', function(done) {
+    var context = {};
+    var value = expect.createSpy().andCall(function() {
+      expect(this).toBe(context);
+    });
+    normalize.bind(context).date(value);
+    expect(value).toHaveBeenCalled();
+    done();
+  });
 });