Merge pull request #7 from tewen/tewen/function-or-value

functionOrValue method added to the library.

.npmignore

@@ -1,3 +1,4 @@
 test/
 .nvmrc
 .eslintrc
+.idea/

README.md

@@ -164,6 +164,19 @@ flattenObject(obj);
 ```
 
 
+#### functionOrValue(fnOrValue, [...args])
+
+Returns either the value given or the return value of the function passed in. Can be called with optional arguments (...args). 
+Also cascades downward if functions return functions.
+
+```JavaScript
+console.log(functionOrValue(true)); // true
+console.log(functionOrValue(() => false)); // false
+console.log(functionOrValue((a, b, c) => a + b + c, 5, 6, 7)); // 18
+console.log(functionOrValue((a, b, c) => () => a + c, 5, 6, 7)); // 12
+```
+
+
 #### isJsonString(str)
 
 Returns a boolean that specifies whether the string is parsable JSON.

lib/function.js

@@ -4,6 +4,11 @@ function acceptNoArguments(fn, ...args) {
   return _.ary(_.partial(fn, ...args), 0);
 }
 
+function functionOrValue(fnOrValue, ...args) {
+  return _.isFunction(fnOrValue) ? functionOrValue(fnOrValue(...args), ...args) : fnOrValue;
+}
+
 module.exports = {
-  acceptNoArguments
+  acceptNoArguments,
+  functionOrValue
 };

test/function.spec.js

@@ -2,7 +2,7 @@ const chai = require('chai');
 const { expect } = chai;
 const sinon = require('sinon');
 
-const { acceptNoArguments } = require('../');
+const { acceptNoArguments, functionOrValue } = require('../');
 
 chai.use(require('sinon-chai'));
 
@@ -36,4 +36,47 @@ describe('function', function () {
       expect(fn.args[0]).to.be.eql([3, 4]);
     });
   });
+
+  describe('functionOrValue()', function () {
+    let fn;
+
+    beforeEach(function () {
+      fn = sinon.stub().returns(55);
+    });
+
+    it('should return a non-function nil value if passed', function () {
+      expect(functionOrValue(null)).to.be.null;
+    });
+
+    it('should return a non-function primitive value of passed', function () {
+      expect(functionOrValue(55)).to.equal(55);
+    });
+
+    it('should return an object if passed', function () {
+      expect(functionOrValue({ name: 'Koolaid' })).to.eql({ name: 'Koolaid' });
+    });
+
+    it('should return an array if passed', function () {
+      expect(functionOrValue([1, 2, 5])).to.eql([1, 2, 5]);
+    });
+
+    it('should call a function even if no additional arguments are passed', function () {
+      expect(functionOrValue(fn)).to.equal(55);
+      expect(fn).to.have.been.calledOnce;
+    });
+
+    it('should call a function with the additional arguments', function () {
+      expect(functionOrValue(fn, 44, {}, 'orange')).to.equal(55);
+      expect(fn).to.have.been.calledOnce;
+      expect(fn).to.have.been.calledWith(44, {}, 'orange');
+    });
+
+    it('should be able to call cascading functions that return other functions', function () {
+      const stub = sinon.stub().returns(true);
+      fn = () => () => () => stub;
+      expect(functionOrValue(fn, 78, [55, 66, 77])).to.be.true;
+      expect(stub).to.have.been.calledOnce;
+      expect(stub).to.have.been.calledWith(78, [55, 66, 77]);
+    });
+  });
 });