feat: add dropArgs

Closes #679

src/dropArgs.js

@@ -0,0 +1,23 @@
+import { nAry } from 'ramda';
+
+/**
+ * Accepts a function with any arity and returns a function with arity of zero.
+ * The returned function ignores any arguments supplied to it.
+ *
+ * @func dropArgs
+ * @memberOf RA
+ * @since {@link https://char0n.github.io/ramda-adjunct/2.10.0|v2.10.0}
+ * @category Logic
+ * @sig (...a -> b)-> () -> b
+ * @param {Function} fn The function with any arity
+ * @return {Function} Returns function with arity of zero
+ * @see {@link http://ramdajs.com/docs/#nAry|R.nAry}
+ * @example
+ *
+ * const fn = (a = 1, b = 2) => a + b;
+ *
+ * RA.dropArgs(fn)(3, 4); //=> 3
+ */
+const dropArgs = nAry(0);
+
+export default dropArgs;

src/index.d.ts

@@ -973,6 +973,12 @@ declare namespace RamdaAdjunct {
         argsPass(combiningPredicate: Function, predicates: Function[]): Function;
         argsPass(combiningPredicate: Function): (predicates: Function[]) => Function;
 
+        /**
+         * Accepts a function with any arity and returns a function with arity of zero.
+         * The returned function ignores any arguments supplied to it.
+         */
+        dropArgs(fn: Function): Function;
+
         /**
          * Creates an array with all falsy values removed.
          * The values false, null, 0, "", undefined, and NaN are falsy.

src/index.js

@@ -154,5 +154,6 @@ export { default as neither } from './neither';
 export { default as notAllPass } from './notAllPass';
 export { default as nonePass } from './nonePass';
 export { default as argsPass } from './argsPass';
+export { default as dropArgs } from './dropArgs';
 // Types
 export { default as Identity } from './fantasy-land/Identity';

test/dropArgs.js

@@ -0,0 +1,27 @@
+import * as R from 'ramda';
+
+import * as RA from '../src';
+import eq from './shared/eq';
+
+describe('dropArgs', function() {
+  let fn;
+  let zeroArityFn;
+
+  beforeEach(function() {
+    fn = (a = 1, b = 2) => a + b;
+    zeroArityFn = RA.dropArgs(fn);
+  });
+
+  it('should drop all arguments', function() {
+    const actual = zeroArityFn('ignore1', 'ignore2');
+    const expected = 3;
+
+    eq(actual, expected);
+  });
+
+  it('should support placeholder to specify "gaps"', function() {
+    const dropArgs = RA.dropArgs(R.__);
+
+    eq(dropArgs(fn)('ignore1', 'ignore2'), 3);
+  });
+});