Javascript Certification

fullstack/javascript/1-variables-strings/exercises/script-regexp.js

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+/*
+1. Remove all non-digits
+str.replace(/\D/g, '')
+"abc123def456" → "123456"
+
+2. Remove all non-alphanumeric (keep letters and numbers)
+str.replace(/[^\w]/g, '')
+"hello-world!" → "helloworld"
+
+3. Remove punctuation (keep letters, numbers, spaces)
+str.replace(/[^\w\s]/g, '')
+"Hello, world!" → "Hello world"
+
+4. Split by one or more spaces
+str.split(/\s+/)
+"hello    world" → ["hello", "world"]
+
+5. Match email pattern
+/[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/g
+
+6. Match hashtags
+/#(\w+)/g
+
+7. Match text between delimiters (non-greedy)
+/\[(.*?)\]/g
+"[abc] [def]" → matches "abc" and "def" separately
+
+8. Check if contains uppercase
+/[A-Z]/.test(str)
+
+9. Check if contains number
+/\d/.test(str)
+
+10. Escape RegExp special characters
+str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
+
+
+Challenge for You
+Find potential bugs in these other solutions I gave you:
+Exercise 13: Title Case Converter
+javascript// Does this handle ALL edge cases?
+const prevWord = words[index - 1];
+if (prevWord && prevWord.endsWith(':')) {
+  return capitalize(word);
+}
+What if:
+
+Input: "title:no space after colon"
+Input: "title: :double colon"
+Input: "title:)emoticon"
+
+Exercise 16: URL Parameter Extractor
+javascript
+const queryString = url.slice(queryIndex + 1);
+What if:
+
+Input: "https://example.com?"
+Input: "https://example.com?key=value=extra"
+Input: "https://example.com?key="
+
+Test these and let me know if you find bugs!
+*/
+
+/* Testing */
+const myName = " Yoandy   88 "
+console.log("Eliminando no digitos:" + myName.replace(/\D/g, ""))
+console.log("Eliminando digitos:" + myName.replace(/\d/g, ""))
+console.log("Eliminando espacios:" + myName.replace(/\s+/g, ""))
+console.log("Eliminando letras - punctuation:" + "Hello, world 22587!".replace(/\D/g, ""))
+
+/*
+Exercise 6: Credit Card Masker
+**Difficulty:** Easy  
+**Objective:** Mask credit card number showing only last 4 digits
+Requirements:
+[x] - Accept string of 16 digits
+[x] - Replace first 12 digits with *
+[x] - Keep spaces if present
+[x] - "1234 5678 9012 3456" becomes "**** **** **** 3456"
+*/
+
+/**
+ * Function that receive a credit card number and apply a mask showing only last 4 digits.
+ * @param {String} cardNumber credit card number with 16 or 19 digits.
+ * @returns credit card number showing only last 4 digits.
+ */
+function maskCreditCard(cardNumber) {
+  // Keep numbers only
+  //const cleaned = cardNumber.replace(/[^0-9]/g, "")
+  const cleaned = cardNumber.replace(/\D/g, "")
+  // check length
+  if (cleaned.length !== 16) {
+    console.log("only digits:" + cleaned)
+    return "Wrong credit card number"
+  }
+  // Mask first 12 digits
+  const masked = "*".repeat(12) + cleaned.slice(-4)
+  // Re-add spaces if original had them
+  if (cardNumber.includes(" ")) {
+    return masked.match(/.{1,4}/g).join(" ")
+  }
+  return masked
+}
+
+// Test cases:
+console.log(`Exercise 6: Credit Card Masker`)
+console.log(maskCreditCard("1234567899876549")) // "************3456"
+console.log(maskCreditCard("1234 5678 9012 3456")) // "**** **** **** 3456"
+// Valid cases
+console.log(maskCreditCard("1234567890123456")) // "************3456"
+console.log(maskCreditCard("1234 9632 9012 3456")) // "**** **** **** 3456"
+console.log(maskCreditCard("4532-1488-0343-6467")) // "**** **** **** 6467"
+
+// Invalid cases
+console.log(maskCreditCard("yoandydobleshola")) // "Wrong credit card number"
+console.log(maskCreditCard("123")) // "Wrong credit card number"
+console.log(maskCreditCard("abcd1234efgh5678")) // "Wrong credit card number"
+console.log(maskCreditCard("")) // "" (string vacío)*/
+console.log("\n==================================\n")
+
+/*
+Find potential bugs in these other solutions I gave you:
+Exercise 13: Title Case Converter
+javascript// Does this handle ALL edge cases?
+const prevWord = words[index - 1];
+if (prevWord && prevWord.endsWith(':')) {
+  return capitalize(word);
+}
+What if:
+
+Input: "title:no space after colon"
+Input: "title: :double colon"
+Input: "title:)emoticon"
+Exercise 13: Title Case Converter (Advanced)
+Difficulty: Hard
+Objective: Convert to title case with English grammar rules
+*/
+
+// Requirements:
+// [x] - Capitalize first and last word always
+// [x] - Capitalize all words except: a, an, the, and, but, or, for, nor, on, at, to, by, in
+// [x] - Articles after colon (:) should be capitalized
+// [x] - "the quick brown fox" → "The Quick Brown Fox"
+// [x] - "a tale of two cities" → "A Tale of Two Cities"
+
+/**
+ * Converts text to title case following English grammar rules
+ * @param {string} text - Text to convert
+ * @returns {string} Title-cased text
+ */
+function toTitleCase(text) {
+  // Words that should remain lowercase (unless first/last/after colon)
+  const exceptions = new Set(["a", "an", "the", "and", "but", "or", "for", "nor", "on", "at", "to", "by", "in", "of"])
+
+  const words = text.trim().toLowerCase().split(/\s+/)
+
+  return words
+    .map((word, index) => {
+      // Always capitalize first and last word
+      if (index === 0 || index === words.length - 1) {
+        return capitalize(word)
+      }
+
+      // Check if previous word ended with colon
+      const prevWord = words[index - 1]
+      if (prevWord && prevWord.endsWith(":")) {
+        return capitalize(word)
+      }
+
+      // Capitalize unless it's an exception word
+      return exceptions.has(word) ? word : capitalize(word)
+    })
+    .join(" ")
+}
+
+/**
+ * Capitalizes first letter of a word
+ * @param {string} word - Word to capitalize
+ * @returns {string} Capitalized word
+ */
+function capitalize(word) {
+  return word.charAt(0).toUpperCase() + word.slice(1)
+}
+// Test cases:
+console.log(`Exercise 13: Title Case Converter (Advanced)`)
+//console.log(toTitleCase("the lord of the rings"))
+// "The Lord of the Rings"
+//console.log(toTitleCase("thE an THE"))
+// "The an The"
+//console.log(toTitleCase("title:no space after colon"))
+//console.log(toTitleCase("title: :double colon"))
+console.log(toTitleCase("title:'-(emotic:(on"))
+// "Javascript"
+//console.log(toTitleCase(" Array sentence: just finished an amazing dayx. "))
+console.log("\n==================================\n")