Javascript - Utilities Flashcards
Write a function which returns another function and execute it after calling
function higherOrderFunction(){
function displayHello(){
console.log("Hello")
}
return displayHello;
}
// driver code var func = higherOrderFunction(); func(); // Hello
Write a function which executes another function recieved as an argument
function callbackExecutor(callback){
if(typeof callback === "function"){
callback();
}
}
// driver code
function callbackFunc(){
console.log("Callback function executed");
}
callbackExecutor(callbackFunc); // Callback function executed
Create a function having no parameters declared and print all the arguments passed to it
(Method1)
function func(){
for(let key in arguments){
console.log(arguments[key]);
}
}
// driver code func(1, "Hello", true);
Create a function having no parameters declared and print all the arguments passed to it
(Method2)
function func(){
for(let value of arguments){
console.log(value);
}
}
// driver code func(1, "Hello", true);
Write a function which executes only if the number of arguments match the number of parameters the function is expecting
function func(a, b, c){
if(func.length === arguments.length){
console.log("Number of arguments passed match the expected arguments");
}
else {
throw new Error("Number of arguments passed do not match the expected arguments");
}
}Design a function which can recieve variable number of arguments in parameters and print them
function varArgsFunc(...params){
params.forEach(function(value, index){
console.log(index, ": ", value);
})
}
// driver code
varArgsFunc("Hello", ",", "World", "!!!");
Write a function which can return multiple values from a function
(Method Array)
function multipleValueReturnFunc(){
const a = 5, b = 10;
return [a, b];
}
// driver code const [x, y] = multipleValueReturnFunc();
Write a function which can return multiple values from a function
(Method Obj)
function multipleValueReturnFunc(){
const a = 'Java', b = 'Script';
return {
a, b
};
}
// driver code
const {x, y} = multipleValueReturnFunc();
Write a function which can return multiple values from a function
(Method Iterator)
function* multipleValueReturnFunc(){
const a = 5, b = 10;
yield a;
yield b;
}
// driver code const iterator = multipleValueReturnFunc(); const x = iterator.next().value; const y = iterator.next().value;
Display all the keys of an object
Method “IN”
for(let key in obj){
if (obj.hasOwnProperty(key)) {
console.log(key);
}
}Display all the keys of an object
Method “OF”
for(let key of Object.keys(obj)){
if (obj.hasOwnProperty(key)) {
console.log(key);
}
}Display all the keys of an object
Method “FOR EACH”
Object.keys(obj).forEach((key) => {
if (obj.hasOwnProperty(key)) {
console.log(key);
}
});Display all the values of an object
console.log(Object.values(obj));
Display all the values of an object
Method “OF Obj”
for(let value of Object.values(obj)){
console.log(value);
}
Display all the values of an object
Method “KEY IN”
for(let key in obj){
if (obj.hasOwnProperty(key)) {
console.log(obj[key]);
}
}Write a function which can check if a given object is empty or not
function isObjectEmpty(obj){
if(obj !== null && typeof obj !== "undefined" && typeof obj === "object")
return Object.keys(obj).length === 0 && JSON.stringify(obj) === "{}";
else
return false;
}Show the usage of ‘Object.entries’ to create an object from key value pairs
(Method “ARRAY”)
const arr = [ ['0', 'a'], ['1', 'b'], ['2', 'c'] ]; const obj = Object.fromEntries(arr);
Show the usage of ‘Object.entries’ to create an object from key value pairs
(Method “MAP”)
const map = new Map([ ['foo', 'bar'], ['baz', 42] ]); const obj = Object.fromEntries(map);
Connect 2 objects so that one object is prototypically connected to the other
(Method “setPrototype”)
const obj1 = { a: 1 };
const obj2 = { b: 2 };
obj2.setPrototypeOf(obj1);Connect 2 objects so that one object is prototypically connected to the other
(Method ‘__porto__’)
const obj1 = { a: "Object 1 value" };
const obj2 = { b: "Object 2 value" };
obj2.\_\_proto\_\_ = obj1;Create an object with getter and setter for property
const obj = {};
Object.defineProperty(obj, 'data', {
_data: 0, // closure variable to hold the data
get() {
return this._data;
},
set(value) {
this._data = value;
}
});
Write a class which uses private variable and function
class ClassWithPrivateFields {
#privateVar;
publicVar;
#privatFunc() {
this.#privateVar = 7;
this.publicVar = 10;
}
publicFunc() {
this.#privatFunc();
return [this.#privateVar, this.publicVar];
}
}
// driver code const instance = new ClassWithPrivateFields();
// can't access private variable instance.privateVar; // undefined
// can’t access private function
instance. privatFunc(); // Error
instance. publicFunc(); // 7, 10
Show how can we use for..of loop to iterate on a range with given start and end values in an object
// Example
let range = {
start: 1,
end: 10
};
for (let i of range) console.log(i); // 1 2 3 4 5 6 7 8 9 10
Write a program to iterate over an array and print all the values of it
(Method “traditional for loop”)
for(let i =0; i < arr.length; i++){
console.log(arr[i]);
}Write a program to iterate over an array and print all the values of it
(Method “IN”)
for(let index in arr){
console.log(arr[index]);
}
Write a program to iterate over an array and print all the values of it
(Method “OF”)
for(let value of arr){
console.log(value);
}
Write a program to append and prepend, single or multiple values in to an array
(Method “single”)
const arr = [2, 3];
arr. push(4); // [2, 3, 4]
arr. unshift(1); // [1, 2, 3, 4]
Write a program to append and prepend, single or multiple values in to an array
(Method “multiple”)
const arr = [3, 4];
arr. push(5, 6); // [3, 4, 5, 6]
arr. unshift(1, 2); // [1, 2, 3, 4, 5, 6]
Write a program to append and prepend, single or multiple values in to an array
(Method “continuous”)
const arr = [1, 2, 3];
const otherArr = [4, 5, 6];
arr.push(…otherArr); // [1, 2, 3, 4, 5, 6]
arr.unshift(…otherArr); // [4, 5, 6, 1, 2, 3, 4, 5, 6]
Show insertion and removal of elements can happen in the array for given index
const arr = [1, 2, 2, 3];
const position = 2;
const count = 1;
arr.splice(position, count); // [2]
console.log(arr); // [1, 2, 3]
Show the different ways of emptying an array which has values
(Method “re-init”)
arr = [];
Show the different ways of emptying an array which has values
(Method “SPLICE”)
arr.splice(0, arr.length)
Check if given input is an array or not
Method “ARRAY”
Array.isArray(arr);
Check if given input is an array or not
Method “OBJECT”
Object.prototype.toString.call(arr) === ‘[object Array]’
Show how an array in JavaScript can act like a stack and queue
// To add the value to the stack arr.push(value);
// To remove the value from the stack arr.pop();
// To remove the value from the queue arr.shift();
Create an array by removing all the holes of the array
const uniqueArr = arr.filter(value => true);
Optimize the given statements having lot of logical checks to use a compact and cleaner logic
browser === “chrome” || browser === “firefox” || browser === “IE” || browser === “safari”
Optimize the given statements having lot of logical checks to use a compact and cleaner logic
(Method “variable INCLUDES”)
const browserList = ["chrome", "firefox", "IE", "safari"]; !browserList.includes(browser);
Write a program to iterate over a 2 dimensional array and print all the values of it
(Method “TRADITIONAL”)
for (let i = 0; i < arr.length; i++) {
for (let j = 0; j < arr[i].length; j++) {
console.log(arr[i][j]);
}
}Write a program to iterate over a 2 dimensional array and print all the values of it
(Method “VAR of ARRAY”)
for (let rowArr of arr) {
for (let value of rowArr) {
console.log(value);
}
}Write a code to make xmlHTTPRequest to get data from the server asynchronously
const xhr = new XMLHttpRequest();
xhr.open("GET", url);
xhr.onload = function() {
console.log(this.response);
};
xhr.onerror = function() {
console.log(this.statusText);
};
xhr.send();
Show the usage of typeof operator on different types of values
typeof 50 // "number"
typeof "text" // "string"
typeof true // "boolean"
typeof undefined // "undefined"
typeof function(){} // "function"
typeof 10n // "bigint"
typeof Symbol() // "symbol"
typeof [1, 2] // "object"
typeof {} // "object"Write a code to iterate over a string
Method “TRADITIONAL”
for(let i =0; i < str.length; i++){
console.log(str.charAt(i));
}Write a code to iterate over a string
Method “VAR in STR”
for(let index in str){
console.log(str[index]);
}
Write a code to iterate over a string
Method ‘VAR of STR”
for(let value of str){
console.log(value);
}
Show the creation of Regular Expression in JavaScript
// literal form let re = /ab+c/g;
// constructor form
let re = new RegExp('ab+c', 'g');
Show the usage of template literals with expression interpolation and tagged templates
// Template literals with expression interpolation
const num1 = 10, num2 = 20;
`The sum of ${num1} and ${num2} is ${num1 + num2}`; // The sum of 10 and 20 is 30
