js-ninja-questions

Questions and Solutions for JS Ninjas

Please feel free to add or update any of the following

Your suggestions for improvement are more than welcome at [email protected]

Questions Here (Solutions are below)

Question 1. Make the following Javascript code work for any number of arguments and combinations

console.info(''+multiply(5, 6));    // 30
console.info(''+multiply(5)(6));    // 30
console.info(''+multiply(5, 2)(3)); // 30
console.info(''+multiply(5)(2)(3)); // 30

Question 2. What will be the following three outputs

var z={},
    y={'0':'nice'},
    x={'1':'nicer'};
z[y] = 0;
z[x] = 1;
console.log(z[y]);
console.log(z[x]);
console.log(z[y] === z[x]);

Question 3. How about the equality checks between the objects with the same content

var a = {'key': 'value'};
var b = {'key': 'value'};
console.info(a == b);
console.info(a === b);

Question 4. Let's implement a getUniqueId with auto incrementing in JS

getUniqueId(); // 1
getUniqueId(); // 2
getUniqueId(); // 3

Question 5. More Questions to be added... 😉

Now Solutions

Solution 1.

var multiply = function() {
  var currentResult = eval(Array.prototype.join.call(arguments, '*'));
  multiply.lastResult = (multiply.lastResult ? (multiply.lastResult*currentResult) : currentResult);
  return multiply;
};
multiply.toString = function() {
  var temp = multiply.lastResult;
  multiply.lastResult = null;
  return temp;
};
//Test Cases
console.info(''+multiply(5, 6));    // 30
console.info(''+multiply(5)(6));    // 30
console.info(''+multiply(5, 2)(3)); // 30
console.info(''+multiply(5)(2)(3)); // 30

Solution 2.

var z={},
    y={'0':'nice'},
    x={'1':'nicer'};
z[y] = 0;
z[x] = 1;
console.log(z[y]);          //1
console.log(z[x]);          //1
console.log(z[y] === z[x]); //true

Solution 3.

var a = {'key': 'value'};
var b = {'key': 'value'};
console.info(a == b);   // false
console.info(a === b);  // false

Solution 4.

Option 1 - Let's thrill with overriding the function itself being inside the function 💀

var getUniqueId = function() {
    var id = 0;
    getUniqueId = function() {
        return ++id;
    };
    return ++id;
};

getUniqueId(); // 1
getUniqueId(); // 2
getUniqueId(); // 3

Option 2 - Using IIFE

var getUniqueId = (function() {
    var id = 0;
    return function() {
        return ++id;
    };
})();

getUniqueId(); // 1
getUniqueId(); // 2
getUniqueId(); // 3

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