Interview Questions- Part-21

power of x ^ y

				
					//Short syntax of power of
console.log(2 ** 5); //32

//using Math operation
console.log(Math.pow(2, 5)); //32

for of usage 

				
					//2.for of usage
let productDetails = [
  {
    product_Id: 1,
    product_Name: "LG Monitor",
    price: "55k",
    rating: "super",
  },
  {
    product_Id: 2,
    product_Name: "LG Curve Monitor",
    price: "45k",
    rating: "Average",
  },
];

for (let obj of productDetails) {
  console.log(JSON.stringify(obj));
}

/*
Basically used to send data to backend server
{"product_Id":1,"product_Name":"LG Monitor","price":"55k","rating":"super"}
{"product_Id":2,"product_Name":"LG Curve Monitor","price":"45k","rating":"Average"}
*/

+ to convert string to number

				
					
// + sign to convert string to number if possible
console.log(200 + "200"); //200200
console.log(200 + +"200"); //400
console.log(200 + +"sda"); //NaN

use strict

				
					//4.Use Strict
/*
1.cant use a variable without let var or const keyword

2.cant use reserve words as variables
let eval =10 

3.cant delete a variable

4.cant delete a function

Best practice always use - 'use strict'

*/
function useStrict() {
  "use strict";
  result = 10; //this cant be done - rule 1
  let eval = 15; //this cant be done - rule 2
  delete result; //this cant be done - rule 3
  delete useStrict; //this cant be done - rule 4
}

Guess the output

				
					/*
error has properties
1.message -->error message
2.name --> tells you which error name it is ...
*/

function tryCatch() {
  let result;
  try {
    result = y / 100;
  } catch (error) {
    console.log(error.message); //y is not defined
    console.log(error.name); //ReferenceError
  }
}
tryCatch();

Throw your own custom error object

				
					function tryCatch1() {
  let result;
  try {
    result = y / 100;
  } catch (error) {
    throw {
      message: "tryCatch() method while division has given this error" + error.message,
      name: "Its a custom error",
    };
  }
}
tryCatch1();

//error in console ->
// Uncaught
// {message: 'tryCatch() method while division has given this errory is not defined', name: 'Its a custom error'}
// message: "tryCatch() method while division has given this errory is not defined"
// name: "Its a custom error"
// [[Prototype]]: Object

Handle All errors

				
					//Good Practice to pull out a method and handle all types of error

function HandleAllError(error) {
  switch (error.name) {
    case "ReferenceError":
      console.log("1.Reference Error::-" + error.message);
      break;
    case "RangeError":
      console.log("2.Range Error::-" + error.message);
      break;
    case "TypeError":
      console.log("3.Type Error::-" + error.message);
      break;
    case "URIError":
      console.log("4.URI Error::-" + error.message);
      break;
    case "SyntaxError":
      console.log("5.Syntax Error::-" + error.message);
      break;
    case "EvalError":
      console.log("6.EvalError::-" + error.message);
      break;
    default:
      console.log("Error type is :" + error.name + " --> Error Message ::- " + error.message);
  }
}

//1.referenceError
const referenceError = () => {
  let finalResult = 0;
  try {
    //y is not defined
    finalResult = y * finalResult;
  } catch (error) {
    HandleAllError(error);
  }
};

//2.RangeError
const rangeError = () => {
  let diceThrow = 7;
  try {
    if (diceThrow <= 1 || diceThrow >= 6)
      throw new RangeError("Dice throw should be between 1 and 6");
  } catch (error) {
    HandleAllError(error);
  }
};

//3.typeError
const typeError = () => {
  try {
    let num = 20;
    //subString cant be done on number ..
    num.subString(1);
  } catch (error) {
    HandleAllError(error);
  }
};

//4.URIError
const uriError = () => {
  let uri = "http://%%%%%ldksjfljsdf ";
  try {
    decodeURI(uri);
  } catch (error) {
    HandleAllError(error);
  }
};

//5.syntaxError
const syntaxError = () => {
  try {
    //single quote is missing
    let confirmation = eval("confirm(' Are you sure you want to proceed)");
  } catch (error) {
    HandleAllError(error);
  }
};

//6.EvalError
//use of eval should be avoided as much as possible..
const evalError = () => {
  try {
    throw new EvalError("eval error");
  } catch (error) {
    HandleAllError(error);
  }
};

referenceError();
rangeError();
typeError();
uriError();
syntaxError();
evalError();

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