@@ -44,3 +44,35 @@ console.log([1,2,3].describe()); // Output: This object has keys: 0, 1, 2
4444// - Use Object.defineProperty to avoid polluting for...in loops.
4545// - Always check if the property exists before defining.
4646// - Avoid in production unless absolutely necessary.
47+ 48+ 49+ // =============================
50+ // Array.prototype Extension Example
51+ // =============================
52+ // WARNING: Modifying Array.prototype is discouraged in production for the same reasons as Object.prototype.
53+ // This is for educational/demo purposes only.
54+ 55+ // Example: Add a custom function to Array.prototype
56+ if ( ! Array . prototype . firstAndLast ) {
57+ Object . defineProperty ( Array . prototype , 'firstAndLast' , {
58+ value : function ( ) {
59+ if ( this . length === 0 ) return { first : undefined , last : undefined } ;
60+ return { first : this [ 0 ] , last : this [ this . length - 1 ] } ;
61+ } ,
62+ enumerable : false
63+ } ) ;
64+ }
65+ 66+ // Usage:
67+ const arr = [ 10 , 20 , 30 , 40 ] ;
68+ console . log ( arr . firstAndLast ( ) ) ; // Output: { first: 10, last: 40 }
69+ 70+ // Chaining with default methods:
71+ const mapped = arr . map ( x => x * 2 ) . firstAndLast ( ) ;
72+ console . log ( mapped ) ; // Output: { first: 20, last: 80 }
73+ 74+ // Works with empty arrays too:
75+ console . log ( [ ] . firstAndLast ( ) ) ; // Output: { first: undefined, last: undefined }
76+ 77+ // Clean up (optional):
78+ // delete Array.prototype.firstAndLast;
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