Add isWeekday code snippets

snippets/isWeekday.md

@@ -0,0 +1,16 @@
+### isWeekday
+
+Results in a boolean representation of a specific date.
+
+Pass the specific date object firstly.
+Use `Date.getDay()` to check weekday then return a boolean.
+
+```js
+const isWeekday = (t = new Date()) => {
+  return t.getDay() >= 1 && t.getDay() <= 5;
+};
+```
+
+```js
+isWeekday(); // true (if current date is 2019-07-19)
+```

tag_database

@@ -172,6 +172,7 @@ isTravisCI:node,intermediate
 isUndefined:type,beginner
 isUpperCase:string,utility,beginner
 isValidJSON:type,json,intermediate
+isWeekday:uncategorized
 isWritableStream:node,type,intermediate
 join:array,intermediate
 JSONtoCSV:array,string,object,advanced

test/isWeekday.test.js

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+const {isWeekday} = require('./_30s.js');
+
+test('isWeekDay is a Function', () => {
+  expect(isWeekday).toBeInstanceOf(Function);
+});
+test('Returns the correct type', () => {
+  expect(typeof isWeekday()).toBe('boolean');
+});
+const friday = new Date('2019-07-19');
+const saturday = new Date('2019-07-20');
+test('Returns true', () => {
+  expect(isWeekday(friday)).toBe(true);
+});
+test('Returns false', () => {
+  expect(isWeekday(saturday)).toBe(false);
+});