What is the role of the let and const keywords in block scope

The let and const keywords were introduced in ECMAScript 6 (ES6) to declare variables in JavaScript with block scope. Block scope means that the variable is only accessible within the block of code where it is defined. This is in contrast to the var keyword, which has function scope or global scope.

1. let keyword:
   • Variables declared with let can be reassigned.
   • They are block-scoped, meaning their scope is limited to the block (enclosed by curly braces) in which they are defined.
   • Example:

                   
                       if (true) {
                           let x = 10;
                           console.log(x); // 10
                         }
                         console.log(x); // ReferenceError: x is not defined                      
                   
               

2. const keyword:
   • Variables declared with const are also block-scoped.
   • Constants declared with const cannot be reassigned once they are initialized.
   • It's important to note that when const is used with objects or arrays, the reference to the object or array cannot be changed, but the properties or elements inside it can be modified.
   • Example:

                   
                       const pi = 3.14;
                       pi = 3.14159; // Error: Assignment to constant variable.
                       
                       const arr = [1, 2, 3];
                       arr.push(4); // This is allowed, as it modifies the array in place.                    
                   
               

Using let and const helps in writing more maintainable and less error-prone code by providing better control over variable scoping and reassignment. It also helps prevent unintended variable reassignments, making your code more predictable.

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