diff --git a/ReferenceBooks/JavaScript-The-Definitive-Guide-Master-The-Worlds-Most-Used-Programming-Language-7th-Edition.pdf b/ReferenceBooks/JavaScript-The-Definitive-Guide-Master-The-Worlds-Most-Used-Programming-Language-7th-Edition.pdf
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diff --git a/Snippets/Strings/lowerCaseConverter.js b/Snippets/Strings/lowerCaseConverter.js
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+// toLowerCase() method changes the string to lowercase letters.
+let favLanguage = "JavasCript";
+console.log(favLanguage.toLowerCase()); // javascript
+let standard = "ECMA";
+console.log(standard.toLowerCase()); // ecma
+let oneMoreLangugae = "PHP";
+console.log(oneMoreLangugae.toLowerCase()); // php
diff --git a/Snippets/Strings/upperCaseConverter.js b/Snippets/Strings/upperCaseConverter.js
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+// toUpperCase() method changes the string to upper letters.
+let favLanguage = "JavasCript";
+console.log(favLanguage.toUpperCase()); // JAVASCRIPT
+let firstName = "ECMA";
+console.log(firstName.toUpperCase()); // ECMA
+let oneMoreLangugae = "Python";
+console.log(oneMoreLangugae.toUpperCase()); // PYTHON