Uncover the JavaScript Interview Question That Stumps 90% of Candidates! | by Adarsh Rai | Medium
In the realm of JavaScript interviews, there are questions that appear simple at first but can unravel complexities when examined closely. One such question involves a common JavaScript method and…
Click
Use
to move to a smaller summary and to move to a larger one
JavaScript Interview Question Insights
- The output of typeof applied to an array is 'object' because arrays are a type of object in JavaScript.
- The length property of a function represents the number of arguments expected by the function, excluding rest parameters and default parameters.
- For a function with no parameters, the length property is 0.
- For a function with one parameter, the length property is 1.
- For a function with three parameters, the length property is 3.
- For a function with rest parameters, the length property counts the parameters before the rest parameter.
- For a function with default parameters, the length property counts up to the first default parameter.
- Arithmetic operations in JavaScript implicitly convert strings to numbers.
- NaN is not equal to any other value, including itself.
- The + operator performs string concatenation when one operand is a string.
- JavaScript implicitly converts numbers to strings when concatenated with strings.
- JavaScript evaluates expressions from left to right.
- Floating-point arithmetic in JavaScript can lead to precision errors.
- Type coercion can cause distinct types to be considered equal.
- An empty array is truthy, while ![] evaluates to false. Therefore, [] == ![] evaluates to true.
JavaScript Output and Explanation
- The output is false because NaN is not equal to any other value, including itself.
- The output is 'object' because null is incorrectly reported as an object by the typeof operator.
- The output is '42' because the + operator is used for concatenation when one operand is a string.
- The output is 'number' because NaN is still considered a number in JavaScript.
- The first console.log outputs true because the + operator coerces the operands to strings. The second console.log outputs false because the === operator performs strict equality comparison.
- The output is 'object' because arrays are a type of object in JavaScript.
- The output is 10 because the string '1' is implicitly converted to a number in JavaScript.
- The first console.log outputs '53' because the + operator performs string concatenation. The second console.log outputs 2 because the - operator coerces the string '5' into a number and performs subtraction.
- The output is false due to floating-point arithmetic precision errors.
- The output is true because JavaScript coerces the empty array [] to true.
- The output is true because despite being different types, JavaScript performs type coercion during comparison.
- The output is '75' because JavaScript evaluates expressions from left to right.
Understanding JavaScript Fundamentals and Higher-Order Functions
- The code outputs the sum of two numbers, which is 7.
- The code defines an arrow function that subtracts one number from another, resulting in 5.
- The code utilizes the map method to double each element in an array, resulting in a new array with doubled values.
- The code defines an arrow function that squares a given number, resulting in 16.
JavaScript Type Coercion and Evaluation Order Summary
- The output of typeof applied to an array is 'object' because arrays are a type of object in JavaScript.
- The length property of a function represents the number of arguments expected by the function, excluding rest parameters and default parameters.
- Arithmetic operations in JavaScript implicitly convert strings to numbers.
- NaN is not equal to any other value, including itself.
- The + operator performs string concatenation when one operand is a string.
- JavaScript evaluates expressions from left to right.
- Floating-point arithmetic in JavaScript can lead to precision errors.
- Type coercion can cause distinct types to be considered equal.
- An empty array is truthy, while ![] evaluates to false. Therefore, [] == ![] evaluates to true.
- The output is 'object' because null is incorrectly reported as an object by the typeof operator.