Javascript Hoisting Interview Questions
Javascript Hoisting Interview Questions
JavaScript hoisting is a concept where the JavaScript interpreter moves all the variable and function declarations to the top of their respective scopes before executing the code. This can cause unexpected results when variables and functions are accessed before they are declared. Some commonly asked interview questions related to hoisting include explaining what hoisting is, why it happens, and how it can be avoided. Other questions may involve providing examples of hoisting and its effects on code execution. It is also important to understand the differences between var, let, and const declarations in relation to hoisting.
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1 - What is hoisting in Javascript?
Answer: Hoisting is a process in Javascript where variable and function declarations are moved to the top of their respective scope by the compiler. This means that variables and functions can be used before they are declared in the code.
2) How does hoisting work?
Answer: During compiling, the Javascript engine moves all variable declarations to the top of their scope, while leaving the assignments in their original place. This means that variables can be accessed and used before they are declared, but their value would be undefined until they are assigned a value.
3) What is the difference between var, let, and const when it comes to hoisting?
Answer: Var variables are hoisted to the top of their scope and can be accessed before they are declared, but their value would be undefined until they are assigned a value. Let and const variables, on the other hand, are hoisted to the top of their block scope, but they cannot be accessed until they are declared.
4) Can function declarations be hoisted in Javascript?
Answer: Yes, function declarations are hoisted to the top of their scope. This means that they can be used before they are declared in the code.
5) What is the difference between function declarations and function expressions when it comes to hoisting?
Answer: Function declarations are hoisted to the top of their scope, while function expressions are not. This means that function declarations can be used before they are declared, but function expressions cannot.
6) How does hoisting affect the order of execution in Javascript?
Answer: Hoisting does not change the order of execution in Javascript. It only changes the order in which variables and functions are declared and initialized.
7) What happens if a variable is declared both globally and locally in a function?
Answer: Local variables take precedence over global variables, so the local variable would be used within the function. However, the global variable would still be accessible outside of the function.
8) Can hoisted variables be reassigned in the code?
Answer: Yes, hoisted variables can be reassigned in the code just like any other variable.
9) What happens if a variable and a function have the same name in a hoisted context?
Answer: The function declaration would take precedence over the variable declaration, as function declarations are hoisted first in Javascript.
10) How does hoisting affect variable scoping?
Answer: Hoisting does not affect variable scoping. Variables declared with var will still have function scope, while variables declared with let or const will have block scope.
11) Can hoisted variables be used within a nested function?
Answer: Yes, hoisted variables can be used within a nested function as long as they are declared in the same scope.
12) What happens if a variable is declared using a function expression?
Answer: Function expressions are not hoisted, so the variable would not be accessible until it is declared in the code.
13) Can hoisting cause any unintended consequences in code?
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Answer: Yes, if variables are used before they are declared, it could lead to unexpected behavior or errors.
14) How can we avoid hoisting issues in code?
Answer: We can avoid hoisting issues by always declaring variables at the top of their scope and declaring functions before using them in the code.
15) Is hoisting unique to Javascript?
Answer: No, hoisting is a concept in many programming languages, but it works differently in each one.
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