JavaScript Quiz
What is the result of the following code?
console.log(1 + “2” + 3 + 4);
a) “1234”
b) “10”
c) “6”
d) “124”
What is the result of the following code?
console.log(typeof null);
a) “object”
b) “null”
c) “undefined”
d) “boolean”
Which of the following is NOT a valid way to declare a variable in JavaScript?
a) let myVar = “hello”;
b) var myVar = “hello”;
c) const myVar = “hello”;
d) myVar = “hello”;
What is the output of the following code?
let arr = [1, 2, 3, 4];
console.log(arr.slice(1, 3));
a) [2, 3]
b) [1, 2]
c) [3, 4]
d) [2, 4]
What is the result of the following code?
const a = 10;
a = 20;
console.log(a);
a) 10
b) 20
c) “const” keyword error
d) “let” keyword error
What is the result of the following code?
let num = 5;
num *= 10;
console.log(num);
a) 5
b) 10
c) 50
d) “num” keyword error
What is the result of the following code?
const obj = { name: “John”, age: 30 };
console.log(obj.name);
a) “John”
b) “age”
c) { name: “John”, age: 30 }
d) “undefined”
What is the output of the following code?
let arr = [1, 2, 3];
arr.push(4);
console.log(arr);
a) [1, 2, 3, 4]
b) [4, 3, 2, 1]
c) [1, 2, 3]
d) [1, 2, 4, 3]
Which of the following is NOT a valid data type in JavaScript?
a) string
b) boolean
c) number
d) float
What is the result of the following code?
console.log(5 == “5”);
a) true
b) false
c) “5” keyword error
d) “==” keyword error
JavaScript ANSWERS
What is the result of the following code?
console.log(1 + “2” + 3 + 4);
Answer: a) “1234”
What is the result of the following code?
console.log(typeof null);
Answer: a) “object”
Which of the following is NOT a valid way to declare a variable in JavaScript?
Answer: d) myVar = “hello”; (this is an assignment statement, not a declaration)
What is the output of the following code?
let arr = [1, 2, 3, 4];
console.log(arr.slice(1, 3));
Answer: a) [2, 3]
What is the result of the following code?
const a = 10;
a = 20;
console.log(a);
Answer: c) “const” keyword error
What is the result of the following code?
let num = 5;
num *= 10;
console.log(num);
Answer: c) 50
What is the result of the following code?
const obj = { name: “John”, age: 30 };
console.log(obj.name);
Answer: a) “John”
What is the output of the following code?
let arr = [1, 2, 3];
arr.push(4);
console.log(arr);
Answer: a) [1, 2, 3, 4]
Which of the following is NOT a valid data type in JavaScript?
Answer: d) float (JavaScript only has one numeric data type, which is “number”)
What is the result of the following code?
console.log(5 == “5”);
Answer: a) true (loose comparison between a number and a string will result in true if their values are equal, regardless of their data type)