Add takeWhile

__tests__/takeWhile.js

@@ -0,0 +1,18 @@
+import { takeWhile } from '../src/index.js';
+
+describe('takeWhile', () => {
+  test('should work', () => {
+    expect(takeWhile([1, 2, 3])).toEqual([1, 2, 3]);
+    expect(takeWhile([1, 2, 3], (n) => n < 3)).toEqual([1, 2]);
+    expect(takeWhile([2, 4, 5, 6, 8], (n) => n % 2 === 0)).toEqual([2, 4]);
+  });
+
+  test('wrong arguments', () => {
+    expect(takeWhile([])).toEqual([]);
+    expect(takeWhile([1, 2, 3], {})).toEqual([1, 2, 3]);
+  });
+
+  test('empty arguments', () => {
+    expect(takeWhile([])).toEqual([]);
+  });
+});

src/index.js

@@ -53,6 +53,7 @@ import sum from './sum.js';
 import tail from './tail.js';
 import take from './take.js';
 import takeRight from './takeRight.js';
+import takeWhile from './takeWhile.js';
 import unary from './unary.js';
 import uniq from './uniq.js';
 import upperFirst from './upperFirst.js';
@@ -111,6 +112,7 @@ export {
   tail,
   take,
   takeRight,
+  takeWhile,
   unary,
   uniq,
   upperFirst,
@@ -170,6 +172,7 @@ export default {
   tail,
   take,
   takeRight,
+  takeWhile,
   unary,
   uniq,
   upperFirst,

src/takeWhile.js

@@ -0,0 +1,31 @@
+// @ts-check
+import isFunction from './isFunction.js';
+import stubTrue from './stubTrue.js';
+
+/**
+ * Creates a `slice` of array with `n` elements taken from the beginning.
+ *
+ * @param {Array} array The array to query.
+ * @param {Function} predicate The function invoked per iteration.
+ * @returns {Array} Returns the slice of `array`.
+ */
+const takeWhile = (array, predicate) => {
+  // TODO: Support matches, matchesProperty and property
+  const processedPredicate = isFunction(predicate) ? predicate : stubTrue;
+
+  const takedItems = [];
+
+  for (let i = 0; i < array.length; i += 1) {
+    const item = array[i];
+
+    if (!processedPredicate(item)) {
+      return takedItems;
+    }
+
+    takedItems.push(item);
+  }
+
+  return takedItems;
+};
+
+export default takeWhile;