Salesforce JavaScript Developer Practice Exam

How does the 'let' keyword differ from 'var' in terms of scope?

1. 'let' has function scope while 'var' does not

2. 'let' has block scope while 'var' has function scope

3. Both behave the same

4. 'var' has block scope while 'let' does not

The correct answer is: 'let' has block scope while 'var' has function scope

The correct answer highlights the key difference between the 'let' and 'var' keywords, which is their scope. 'Let' is scoped to the nearest enclosing block, meaning that if you declare a variable using 'let' inside a set of curly braces (such as within an if statement or a loop), that variable is only accessible within that block. This prevents the variable from being accessed outside those braces, which promotes better encapsulation and avoids accidental variable modifications from outside the intended scope. On the other hand, 'var' is function-scoped. This means that if you declare a variable using 'var' inside a function, it's accessible throughout the entire function, regardless of how many nested blocks there are within it. If 'var' is declared outside of any function, it becomes a global variable, accessible from anywhere in the code after its declaration. This distinction leads to differences in behavior, especially in scenarios involving loops or conditionals where variables might need to have scoped visibility. In modern JavaScript development, 'let' and 'const' are favored over 'var' due to these enhancements in variable scoping, which help reduce potential errors and increase code maintainability.