Javascript Interview Coding Exercises
JavaScript Interview Coding Exercises: Comprehensive Guide for Preparation
JavaScript interview coding exercises are commonly used in technical interviews to assess a candidate's problem-solving skills and knowledge of the programming language. These exercises typically involve providing a coding challenge or problem, and the candidate is expected to write a solution using JavaScript within a given time frame. They can cover a range of topics, such as data manipulation, algorithm design, object-oriented programming, and more. These exercises not only test the candidate's technical abilities but also their ability to think critically and efficiently under pressure. They are an effective way for employers to evaluate the candidate's proficiency in JavaScript and their potential for success in a technical role.
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1 - Explain the difference between let, var, and const in JavaScript.
Let is a block scoped variable, which means it is limited to the block of code it is declared in. Var is a function scoped variable, which means it is accessible throughout the function it is declared in. Const is also block scoped but its value cannot be reassigned after it is declared.
2) What is the difference between == and === in JavaScript?
== is used for loose comparison and only compares the values, whereas === is used for strict comparison and also compares the data types.
3) What is hoisting in JavaScript?
Hoisting is a mechanism in JavaScript where variable and function declarations are moved to the top of their scope. In simpler terms, it means that variables and functions can be referenced before they are declared.
4) How would you check if a variable is an array in JavaScript?
We can use the isArray() method to check if a variable is an array. It returns true if the variable is an array, otherwise it returns false.
5) Explain the concept of closures in JavaScript.
Closures are functions that have access to variables declared in their outer scope. This means that even after the outer function has returned, the inner function still has access to the variables from the outer scope.
6) What is the difference between the apply() and call() methods in JavaScript?
Both methods are used to call a function with a specified value for the ‘this’ keyword. The only difference is that apply() takes in an array of arguments, while call() takes in a list of arguments.
7) What is the difference between let and var in terms of scope?
As mentioned earlier, let has block scope while var has function scope. This means that a variable declared with let is only accessible in the block it is declared in, while a variable declared with var is accessible throughout the function it is declared in.
8) What are the different data types in JavaScript?
JavaScript has six primitive data types: string, number, boolean, null, undefined, and symbol (added in ES6). It also has a complex data type which is object.
9) How would you loop through an array in JavaScript?
There are multiple ways to loop through an array in JavaScript, the most common being the for loop and forEach() method. The for loop allows you to access each element in an array using its index, while the forEach() method allows you to iterate through the array and perform a function on each element.
10) Explain the concept of prototype in JavaScript.
Every object in JavaScript has a prototype, which is an object from which it inherits properties and methods. Any changes made to the prototype of an object will be reflected in all instances of that object.
11) What is a higher order function in JavaScript?
A higher order function is a function that takes in another function as an argument, or returns a function as a result. This concept is often used in functional programming.
12) What is the difference between a null value and an undefined value?
A null value is explicitly assigned by a programmer to indicate that a variable has no value. An undefined value is a default value for variables that have not been assigned a value yet.
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13) How would you remove the first and last element from an array in JavaScript?
We can use the shift() method to remove the first element and the pop() method to remove the last element from an array.
14) Explain the concept of event bubbling in JavaScript.
Event bubbling is a phenomenon where an event triggered on a child element is also triggered on its parent elements, all the way up to the root element. This can cause unwanted effects and can be prevented by using event.stopPropagation().
15) What is the difference between == and === in terms of type coercion?
== allows for type coercion, which means it will try to change the data type of one of the operands to match the other, while === does not allow type coercion and strictly compares both the values and data types.
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