100 Nodejs Interview Questions
Post Date : 2022-10-11T14:30:39+07:00
Modified Date : 2022-10-11T14:30:39+07:00
Category: cheatsheet
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Question 1 : NodeJS Write Stream
In the JavaScript file, write a program to perform a GET request on the route https://coderbyte.com/api/challenges/json/age-counting which contains a data key and the value is a string which contains items in the format: key=STRING, age=INTEGER. Your goal is to count how many items exist that have an age equal to 32. Then you should create a write stream to a file called output.txt and the contents should be the key values (from the json) each on a separate line in the order they appeared in the json file (the file should end with a newline character on its own line). Finally, then output the SHA1 hash of the file.
Example Input
{
"data": "key=IAfpK, age=32, key=WNVdi, age=64, key=jp9zt, age=40, key=9snd2, age=32"
}
File Contents (output.txt)
IAfpK
9snd2
Example Output
7caa78c7180ea52e5193d2b4c22e5e8a9e03b486
Question 2 : NodeJS Counting age
In the JavaScript file, write a program to perform a GET request on the route https://coderbyte.com/api/challenges/json/age-counting which contains a data key and the value is a string which contains items in the format: key=STRING, age=INTEGER. Your goal is to count how many items exist that have an age equal to or greater than 50, and print this final value.
Example Input
{ "data": "key=IAfpK, age=58, key=WNVdi, age=64, key=jp9zt, age=47" }
Example Output
2
Question 3 : NodeJS Print Files
In the JavaScript file, write a program to first create a file in the current directory with the name newfile.txt filled with any content. Then, using exec, print to the console all the files in the current directory so that they are in the following format: FILENAME, FILENAME, …
Example output
file.js, helloworld.txt, abc.txt
Question 4: NodeJS REST GET Simple
In the JavaScript file, write a program to perform a GET request on the route https://coderbyte.com/api/challenges/json/rest-get-simple and then print to the console the hobbies property in the following format: ITEM1, ITEM2, …
Example Output
running, painting
const https = require("https");
https.get(
"https://coderbyte.com/api/challenges/json/rest-get-simple",
(resp) => {
let rawData = "";
// parse json data here...
resp.on("data", (chunk) => {
rawData += chunk;
});
resp.on("end", () => {});
}
);
Question 5: Write a factorial function
// factorial is a function that multiples a number by every number below it till 1
const factorialCalculation = (n) => {};
Answer
// factorial is a function that multiples a number by every number below it till 1
const factorialCalculation = (n) => {
if (isNaN(n) || n.toString().indexOf(".") > 0 || n < 0) {
throw new Error(`${n} is not a natural number`);
}
// n <= 1 : 0,1
if (n <= 1) {
return 1;
}
if (n >= 1e3) {
throw new Error(`n is too large, it must be less than ${1e3}`);
}
let factorialResult = n;
for (let i = n - 1; i > 1; factorialResult *= i--);
return factorialResult;
};
console.log(0, factorialCalculation(0));
console.log(2.0, factorialCalculation(2.0));
console.log(3, factorialCalculation(3));
console.log(4, factorialCalculation(4));
console.log(5, factorialCalculation(5));
console.log(6, factorialCalculation(6));
console.log(1e2, factorialCalculation(1e2));
console.log("10", factorialCalculation("10"));
console.log("5", factorialCalculation("5"));
console.log(2.3, factorialCalculation(2.3));
console.log("a", factorialCalculation("a"));
console.log(1e99, factorialCalculation(1e9));
console.log(-2, factorialCalculation(-2));
Question 6: Binary Gap
A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ends in the binary representation of N.
For example, number 9 has binary representation 1001 and contains a binary gap of length 2. The number 529 has binary representation 1000010001 and contains two binary gaps: one of length 4 and one of length 3. The number 20 has binary representation 10100 and contains one binary gap of length 1. The number 15 has binary representation 1111 and has no binary gaps. The number 32 has binary representation 100000 and has no binary gaps.
Write a function:
function solution(N);
that, given a positive integer N, returns the length of its longest binary gap. The function should return 0 if N doesn’t contain a binary gap.
For example, given N = 1041 the function should return 5, because N has binary representation 10000010001 and so its longest binary gap is of length 5. Given N = 32 the function should return 0, because N has binary representation ‘100000’ and thus no binary gaps.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..2,147,483,647].
Answer
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(N) {
// write your code in JavaScript (Node.js 14)
try {
const MAX_N = 2147483647;
// if not a positive integer return 0
if (isNaN(N) || N <= 0 || N.toString().includes(".") || parseInt(N) > MAX_N)
return 0;
// convert to binary number
// 12 -> 6 -> 3 -> 2 -> 1 => 10000
let cloneOfN = N;
let longestBinaryGap = 0;
let startGap = -1;
let endGap = -1;
for (let index = 0; cloneOfN >= 1; ) {
// set startGap when startGap === -1 cloneOfN %2 === 1
if (cloneOfN % 2 === 1) {
if (startGap === -1) {
startGap = index;
} else if (startGap !== -1 && endGap === -1) {
endGap = index;
// closeGap and compare
const gapDiff = endGap - startGap - 1;
if (gapDiff > longestBinaryGap) {
longestBinaryGap = gapDiff;
}
// reset gap
startGap = index;
endGap = -1;
}
}
cloneOfN = (cloneOfN - (cloneOfN % 2)) / 2;
index++;
}
return longestBinaryGap;
} catch {
return 0;
}
}
console.log(solution(1041));
console.log(solution("abc"));
function solution2(N) {
// write your code in JavaScript (Node.js 14)
try {
const MAX_N = 2147483647;
// if not a positive integer return 0
if (isNaN(N) || N <= 0 || N.toString().includes(".") || parseInt(N) > MAX_N)
return 0;
// convert to binary number
// 12 -> 6 -> 3 -> 2 -> 1 => 10000
let binaryOfN = N.toString(2);
let longestBinaryGap = 0;
let startGap = -1;
let endGap = -1;
for (let index = 0; index < binaryOfN.length; index++) {
// set startGap when startGap === -1 cloneOfN %2 === 1
if (binaryOfN.charAt(index) == 1) {
if (startGap === -1) {
startGap = index;
} else if (startGap !== -1 && endGap === -1) {
endGap = index;
// closeGap and compare
const gapDiff = endGap - startGap - 1;
if (gapDiff > longestBinaryGap) {
longestBinaryGap = gapDiff;
}
// reset gap
startGap = index;
endGap = -1;
}
}
}
return longestBinaryGap;
} catch {
return 0;
}
}
Question 7: Write code to make this become true
// So what is a
if (a == 1 && a == 2 && a == 3) {
console.log("Hello World!");
}
Answer
const a = {
i: 1,
toString: function () {
return a.i++;
},
};
Question 8: Array
Create pairs of an integer array. Each array element may belong to one pair only. Is it possible to use all the integers?
function solutionA(A) {
// return whether it is possible to split all the integers into pair
}
Sample test cases:
- A = [1,2,2,1] => return True. Because we have 2 pairs: [A[0],A[3]], [A[1],A[2]]
- A = [7,7,7] => return False. have a single 7 left
- A = [1,2,2,3] => return false. there’s nothing a[1] can be paired with
Assumptions:
- Length of A : [1..100,000]
- Each element in A is an integer within the range [-1,000,000..1,000,000]
Answer
// Create pairs of an integer array.
// Each array element may belong to one pair only.
// Is it possible to use all the integers?
// return whether it is possible to split all the integers into pair
function solutionA(A) {
// A's length is odd number return false
if (A.length == 0 || A.length % 2 != 0) return false;
let sortedA = A.sort((a, b) => a - b);
// if there is any number in even index is not equal its next number in the sorted array
// it meaned it can not be paired
for (let i = 0; i <= sortedA.length - 1; i += 2) {
if (A[i] != A[i + 1]) return false;
}
return true;
}
// run test
console.log(solutionA([]));
console.log(solutionA([1, 2, 2, 1]));
console.log(solutionA([7, 7, 7]));
console.log(solutionA([1, 2, 2, 3]));
const longestA = [];
for (let i = 0; i < 500, 000; i++) {
longestA.push(-100, 000 + i * 10);
longestA.push(-100, 000 + i * 10);
}
Array.prototype.shuffle = function () {
return this.sort(() => Math.random() - 0.5);
};
console.log(solutionA(longestA.shuffle()));
Question 9
Write typeCheck function
string: string type
int 12.00 and 12 are both integers
float : for example 12.34
number: any int or float
bool: for example true
types are optional and validation should be skipped if the type isn't specified.
\_ always precedes the type name
const obj = {
age_int: 2,
name_string: "Adam",
job: null,
};
const validateObject = typeCheck(obj);
// validateObject.age_int = 2.5; // throws error
validateObject.age_int = 2;
validateObject.job = "fireman";
// validateObject.address_string = 20; // throws error
validateObject.salary_float = 2500.55;
validateObject.worked_experience_number = 10;
validateObject.is_active_bool = false;
console.log(JSON.stringify(validateObject));
const obj_2 = {
employed_bool: "true",
};
const validateObject2 = typeCheck(obj_2); // throws error
console.log(validateObject2);
Answer
const ALLOW_PROP_TYPES = ["string", "int", "float", "number", "bool"];
const propTypes = {
check: (prop, value) => {
if (prop.includes("_") && prop.split("_").length > 1) {
const propParts = prop.split("_");
const dataType = propParts[propParts.length - 1];
if (ALLOW_PROP_TYPES.includes(dataType)) {
// run validation
if (Reflect.has(propTypes, dataType) && !propTypes[dataType](value)) {
throw new Error(`${value} is invalid ${dataType}`);
}
}
}
return true;
},
string: (v) => {
return typeof v === "string";
},
int: (v) => {
return typeof v === "number" && v % 1 === 0;
},
float: (v) => {
return typeof v === "number" && v % 1 !== 0;
},
bool: (v) => {
return typeof v === "boolean";
},
number: (v) => {
return typeof v === "number";
},
};
const typeCheck = (obj) => {
Reflect.ownKeys(obj).map((prop) => {
propTypes.check(prop, obj[prop]);
});
return new Proxy(obj, {
set(obj, prop, value) {
propTypes.check(prop, value);
obj[prop] = value;
return true;
},
});
};
Question 10 : Mark duplicated file
You will have an array of files like this. Your mission is marking the duplicated file.
const files = [
{
id: 1,
name: "abc.pdf",
},
{ id: 2, name: "bcd.pdf" },
{ id: 3, name: "cef.pdf" },
{ id: 4, name: "abc.pdf" },
{ id: 5, name: "abcd.pdf" },
{ id: 6, name: "abcd.pdf" },
{ id: 7, name: "abc.pdf" },
];
Expected output
const expectedOutput = [
{
id: 1,
name: "abc.pdf",
duplicated: false,
},
{ id: 2, name: "bcd.pdf", duplicated: false },
{ id: 3, name: "cef.pdf", duplicated: false },
{ id: 4, name: "abc.pdf", duplicated: true },
{ id: 5, name: "abcd.pdf", duplicated: false },
{ id: 6, name: "abcd.pdf", duplicated: true },
{ id: 7, name: "abc.pdf", duplicated: true },
];
Answer 1
let transformedFiles = [];
files.map((f) => {
let transformedFile = { ...f, duplicated: false };
if (transformedFiles.find((file) => f.name === file.name)) {
transformedFile.duplicated = true;
}
transformedFiles.push(transformedFile);
});
Answer 2
let transformedFiles = files.sort((a, b) => a.name.localeCompare(b.name));
transformedFiles = transformedFiles.map((f, index) => {
if (index === 0)
return {
...f,
duplicated: false,
};
if (f.name.localeCompare(transformedFiles[index - 1].name) === 0)
return {
...f,
duplicated: true,
};
return {
...f,
duplicated: false,
};
});
transformedFiles.sort((a, b) => a.id - b.id).map((f) => console.log(f));