Comprehensive Guide to Arrays in JavaScript: Creation, Methods, and Concepts

Comprehensive Guide to Arrays in JavaScript: Creation, Methods, and Concepts

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  Prepared By: KaleJ. N. Arrays in Java Script 1. What is an Array? An array is a special variable that can hold multiple values. Example: let numbers = [10, 20, 30, 40]; 2. Creating Arrays Method 1: Array Literal let fruits = ["Apple", "Banana", "Mango"]; Method 2: Using new Array() let nums = new Array(1, 2, 3, 4); 3. Accessing Elements let arr = ["A", "B", "C"]; arr[0]; arr[arr.length - 1]; 4. Array Property length let arr = [1,2,3]; arr.length; // 3 5. Modifying Arrays push() - Add at end unshift() - Add at beginning pop() - Remove from end shift() - Remove from beginning 6. Looping Through Arrays For Loop for(let i = 0; i < arr.length; i++){ console.log(arr[i]); } for...of for(let value of arr){ console.log(value); }
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  Prepared By: KaleJ. N. forEach() arr.forEach(function(item){ console.log(item); }); 7. Important Array Methods map() - Creates new array It is an array method that:  Iterates over each element  Applies a function to each element  Returns a new array  Does NOT modify the original array filter() - Filters elements filter() is an array method that:  Iterates over each element  Checks a condition  Returns a new array with only elements that satisfy the condition  Does NOT modify the original array reduce() - Reduces to single value reduce() is an array method that:  Iterates over each element  Combines all elements into one single value  Returns a single output (number, object, array, string, etc.)  Does NOT modify the original array  It is used for sum, product, grouping, counting, flattening, etc. sort() - Sorts array reverse() - Reverses array
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  Prepared By: KaleJ. N. 8. Spread Operator The spread operator […] is used to expand elements of an array into individual values. It helps in copying arrays, merging arrays, and adding new elements without modifying the original array. Example: let arr2 = [...arr1, 4, 5]; → Creates a new array by copying arr1 elements and adding 4 and 5. 9. Destructuring Destructuring is a feature in JavaScript that allows you to extract values from arrays or objects and assign them to variables in a simple way. let [a, b] = [10, 20]; 10. Important Concepts - Arrays are objects - Dynamic size - Can store mixed data types 11. Shallow vs Deep Copy Shallow Copy: let arr2 = arr1; This does not create a new array. It only copies the reference (memory address). Both arr1 and arr2 point to the same array. Proper Copy: let arr2 = [...arr1]; This creates a new array and copies elements.