[ADD] drop

README.md

@@ -37,4 +37,7 @@ const func = $.partialFunction((arg1, arg2) => {
   return arg1;
 });
 const result = func(arg1, arg2); // 1
+
+const func2 = $.partialFunction((arg1) => arg1 > 0, (arg) => arg);
+func2.isDefinedAt(10); // true
 ```

drop/index.js

@@ -0,0 +1,11 @@
+module.exports = function drop(iterable, n) {
+  const dropped = [];
+  let dropping = 0;
+  for (const element of iterable) {
+    if (dropping >= n) {
+      dropped.push(element);
+    }
+    dropping++;
+  }
+  return dropped;
+};

index.js

@@ -3,6 +3,7 @@ const andThen = require('./andThen');
 const any = require('./any');
 const compose = require('./compose');
 const distinct = require('./distinct');
+const drop = require('./drop');
 const filter = require('./filter');
 const foldLeft = require('./foldLeft');
 const foldRight = require('./foldRight');
@@ -17,6 +18,7 @@ module.exports = {
   any,
   compose,
   distinct,
+  drop,
   filter,
   foldLeft,
   foldRight,

test/drop.test.js

@@ -0,0 +1,37 @@
+const assert = require('assert');
+const $ = require('../');
+
+describe('drop test', () => {
+  const array = [3, 4, 5, 6, 7, 8, 9];
+  it('work with array', () => {
+    const result = $.drop(array, 3);
+    assert.deepEqual(result, [6, 7, 8, 9]);
+  });
+  it('work with Set', () => {
+    const set = new Set(array);
+    const result = $.drop(set, 2);
+    assert.deepEqual(result, [5, 6, 7, 8, 9]);
+  });
+  it('work with generator', () => {
+    function* zeroToTen() {
+      for (let i = 0; i <= 10; i++) {
+        yield i;
+      }
+    }    
+    const result = $.drop(zeroToTen(), 3);
+    assert.deepEqual(result, [3, 4, 5, 6, 7, 8, 9, 10]);
+  });
+  it('work with Map', () => {
+    const map = new Map();
+    for (let i = 3; i <= 9; i++) {
+      map.set(i, i * 2);
+    }
+    const result = $.drop(map, 4);
+    assert.deepEqual(result, [[7, 14], [8, 16], [9, 18]]);
+  });
+  it('work with string', () => {
+    const str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
+    const result = $.drop(str, 10).join('');
+    assert.equal(result, 'KLMNOPQRSTUVWXYZ');
+  });
+});