adds nullish_coalescing

Author: ishtms

chapters/04.2_nullish_coalescing.js

@@ -0,0 +1,88 @@
+/**
+ * ========================================================
+ * Nullish Coalescing Operator (??)
+ * ========================================================
+ * The nullish coalescing operator (??) is a logical operator that returns the right-hand operand
+ * when the left-hand operand is null or undefined; otherwise, it returns the left-hand operand.
+ */
+
+/**
+ * ========================================================
+ * Basic Usage
+ * ========================================================
+ * It is often used to assign default values to variables.
+ */
+const name = null;
+const defaultName = "John Doe";
+const username = name ?? defaultName;
+console.log(`Username: ${username}`); // Output: 'Username: John Doe'
+
+/**
+ * ========================================================
+ * Difference from Logical OR (||)
+ * ========================================================
+ * The nullish coalescing operator only checks for null or undefined,
+ * while the logical OR operator (||) checks for any falsy value.
+ */
+const zeroValue = 0;
+const orResult = zeroValue || "default";
+const nullishResult = zeroValue ?? "default";
+console.log(`OR Result: ${orResult}`); // Output: 'OR Result: default'
+console.log(`Nullish Result: ${nullishResult}`); // Output: 'Nullish Result: 0'
+
+/**
+ * ========================================================
+ * Combining with Ternary Operator
+ * ========================================================
+ * The nullish coalescing operator can be combined with the ternary operator for more complex conditions.
+ */
+const age = null;
+const ageValue = age ?? (age === 0 ? "Zero" : "Undefined");
+console.log(`Age Value: ${ageValue}`); // Output: 'Age Value: Undefined'
+
+/**
+ * ========================================================
+ * Use in Object Properties
+ * ========================================================
+ * You can also use it to provide default values for object properties.
+ */
+const user = {
+    firstName: "Jane",
+};
+const lastName = user?.lastName ?? "Doe";
+console.log(`User's Last Name: ${lastName}`); // Output: 'User's Last Name: Doe'
+
+/**
+ * ========================================================
+ * Nuances and Advanced Techniques
+ * ========================================================
+ */
+
+/**
+ * 1. Short-Circuiting
+ * --------------------
+ * Similar to other logical operators, the nullish coalescing operator short-circuits,
+ * meaning it won't evaluate the right-hand expression if it doesn't need to.
+ */
+
+/**
+ * 2. Operator Precedence
+ * ----------------------
+ * Be cautious with operator precedence when combining nullish coalescing with other operators.
+ * Using parentheses can help make the behavior explicit.
+ */
+const result = 5 + (null ?? 2); // This will be 5 + 2 = 7
+
+/**
+ * 3. Type Considerations
+ * -----------------------
+ * Nullish coalescing is useful for avoiding unexpected type conversions,
+ * particularly when dealing with possible null or undefined values.
+ */
+
+/**
+ * 4. Use Cases
+ * ------------
+ * It's commonly used in function arguments, object destructuring, and variable assignments
+ * to provide default values only when a variable is null or undefined, but not for other falsy values.
+ */