merge: Improved pangram algorithm using regular expressions (TheAlgorithms#906)

* feat: used regex instead of Set

* docs: add js doc

* docs: add comments of workable code

* style: format via standardJs

* docs: add details explanation of pangram regex

* docs: add example

* feat: add two implemetaion of

The first implementation with regex and second via HashSet & add the test code for both

* chore: add QNA format of **Pangram**

* style: format with standardJs

* resolve: removed 'Ans'

Author: fahimfaisaal

String/CheckPangram.js

@@ -1,22 +1,54 @@
-/*
-  Pangram is a sentence that contains all the letters in the alphabet
-  https://en.wikipedia.org/wiki/Pangram
+/**
+ * What is Pangram?
+ * Pangram is a sentence that contains all the letters in the alphabet https://en.wikipedia.org/wiki/Pangram
  */
 
-const checkPangram = (string) => {
+/**
+ * @function checkPangramRegex
+ * @description - This function check pangram with the help of regex pattern
+ * @param {string} string
+ * @returns {boolean}
+ * @example - checkPangramRegex("'The quick brown fox jumps over the lazy dog' is a pangram") => true
+ * @example - checkPangramRegex('"Waltz, bad nymph, for quick jigs vex." is a pangram') => true
+ */
+const checkPangramRegex = (string) => {
+  if (typeof string !== 'string') {
+    throw new TypeError('The given value is not a string')
+  }
+
+  /**
+   * Match all 26 alphabets using regex, with the help of:
+   * Capturing group - () -> Groups multiple tokens together and creates a capture group for extracting a substring or using a backreference.
+   * Character set - [a-z] -> Matches a char in the range a to z in case-insensitive for the 'i' flag
+   * Negative lookahead - (?!) -> Specifies a group that can not match after the main expression (if it matches, the result is discarded).
+   * Dot - . -> Matches any character except linebreaks. Equivalent to
+   * Star - * -> Matches 0 or more of the preceding token.
+   * Numeric reference - \{$n} -> Matches the results of a capture group. E.g. - \1  matches the results of the first capture group & \3 matches the third.
+ */
+  return string.match(/([a-z])(?!.*\1)/gi).length === 26
+}
+
+/**
+ * @function checkPangramSet
+ * @description - This function detect the pangram sentence by HashSet
+ * @param {string} string
+ * @returns {boolean}
+ */
+const checkPangramSet = (string) => {
   if (typeof string !== 'string') {
     throw new TypeError('The given value is not a string')
   }
 
-  const frequency = new Set()
+  const lettersSet = new Set()
 
-  for (const letter of string.toLowerCase()) {
-    if (letter >= 'a' && letter <= 'z') {
-      frequency.add(letter)
+  for (const letter of string.toUpperCase()) {
+    if (/[A-Z]/.test(letter)) {
+      // if the letter is a valid uppercase alphabet then the add method insert the letter to the HashSet
+      lettersSet.add(letter)
     }
   }
 
-  return frequency.size === 26
+  return lettersSet.size === 26
 }
 
-export { checkPangram }
+export { checkPangramRegex, checkPangramSet }

String/test/CheckPangram.test.js

@@ -1,33 +1,65 @@
-import { checkPangram } from '../CheckPangram'
+import { checkPangramRegex, checkPangramSet } from '../CheckPangram'
 
-describe('checkPangram', () => {
+describe('Testing checkPangramRegex function', () => {
   it('"The quick brown fox jumps over the lazy dog" is a pangram', () => {
     expect(
-      checkPangram('The quick brown fox jumps over the lazy dog')
-    ).toBeTruthy()
+      checkPangramRegex('The quick brown fox jumps over the lazy dog')
+    ).toBe(true)
   })
 
   it('"Waltz, bad nymph, for quick jigs vex." is a pangram', () => {
-    expect(checkPangram('Waltz, bad nymph, for quick jigs vex.')).toBeTruthy()
+    expect(checkPangramRegex('Waltz, bad nymph, for quick jigs vex.')).toBe(true)
   })
 
   it('"Jived fox nymph grabs quick waltz." is a pangram', () => {
-    expect(checkPangram('Jived fox nymph grabs quick waltz.')).toBeTruthy()
+    expect(checkPangramRegex('Jived fox nymph grabs quick waltz.')).toBe(true)
   })
 
   it('"My name is Unknown" is NOT a pangram', () => {
-    expect(checkPangram('My name is Unknown')).toBeFalsy()
+    expect(checkPangramRegex('My name is Unknown')).toBe(false)
   })
 
   it('"The quick brown fox jumps over the la_y dog" is NOT a pangram', () => {
     expect(
-      checkPangram('The quick brown fox jumps over the la_y dog')
-    ).toBeFalsy()
+      checkPangramRegex('The quick brown fox jumps over the la_y dog')
+    ).toBe(false)
   })
 
   it('Throws an error if given param is not a string', () => {
     expect(() => {
-      checkPangram(undefined)
+      checkPangramRegex(undefined)
+    }).toThrow('The given value is not a string')
+  })
+})
+
+describe('Testing checkPangramSet function', () => {
+  it('"The quick brown fox jumps over the lazy dog" is a pangram', () => {
+    expect(
+      checkPangramSet('The quick brown fox jumps over the lazy dog')
+    ).toBe(true)
+  })
+
+  it('"Waltz, bad nymph, for quick jigs vex." is a pangram', () => {
+    expect(checkPangramSet('Waltz, bad nymph, for quick jigs vex.')).toBe(true)
+  })
+
+  it('"Jived fox nymph grabs quick waltz." is a pangram', () => {
+    expect(checkPangramSet('Jived fox nymph grabs quick waltz.')).toBe(true)
+  })
+
+  it('"My name is Unknown" is NOT a pangram', () => {
+    expect(checkPangramSet('My name is Unknown')).toBe(false)
+  })
+
+  it('"The quick brown fox jumps over the la_y dog" is NOT a pangram', () => {
+    expect(
+      checkPangramSet('The quick brown fox jumps over the la_y dog')
+    ).toBe(false)
+  })
+
+  it('Throws an error if given param is not a string', () => {
+    expect(() => {
+      checkPangramSet(undefined)
     }).toThrow('The given value is not a string')
   })
 })