Introduction
Namaste, In this blog post I will discuss 7 common FAQs on JS Fundamentals
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Identify the output of the below program
let mydata = "data" / 2; console.log("mydata", mydata);a. Error
b. data
c. undefined
d. NaN
Answer: d
Reason: The string is coerced into a number which is NaN and the division of NaN is NaN.
Identify the output of the below program
let mydata = "data" / 2; console.log("type", typeof mydata);a. number
b. string
c. undefined
d. Error
Answer: a
Reason: NaN is a number type
Identify the output of the below program
let mydata = true/false; console.log("mydata", mydata);a. 1
b. 0
c. Infinity
d. Error
Answer: c
Reason: The true is coerced to 1 and the false to 0. Hence the division of 1/0 is
Infinity in Javascript.
Identify the output of the below program
console.log(typeof boolean, typeof number, typeof string);a. boolean, number, string
b. null, null, null
c. Error
d. undefined, undefined, undefined
Answer: d
Reason: The boolean, number and string are not primitives. They are also not declared and hence undefined for all.
Identify the output of the below program
console.log(typeof Infinity, typeof NaN);a. Error
b. number, number
c. undefined, undefined
d. null, null
Answer: b
Reason: Infinity and NaN are number types.
Identify the output of the below program
let mydata= 100n console.log(typeof mydata, mydata);a. number, 100
b. string, 100n
c. bigint, 100n
d. Error
Answer: c
Reason: Integer values suffixed with n is identified as bigint.
Identify the output of the below program
console.log(typeof typeof);a. number
b. string
c. undefined
d. Error
Answer: d
Reason: Since typeof is an operator and the operand passed to it is also typeof, it is considered an invalid operand (because is it pre-defined).