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Glad to hear that. Thank you Sasikumar Reddy Chevvu🙏
Chety Thanks, that will work but it's always good to use strict comparison inside if condition to avoid type coercion like this:
if (b !== undefined) { // if b provided
return a * b;
}
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Today we will see a frequently asked Javascript interview question.
The question goes like this:
Implement a
productmethod that will return the product of two numbers when invoked using any of the following two ways
This is a very famous Javascript interview question because it tests your knowledge of functional Javascript, closures, and function arguments. To solve this, let’s understand some basic concepts.
A higher order function is a function which either accepts a function, returns a function or both.
For Example: Array map, filter, reduce methods all accept a function as an argument and are higher order functions.
When a function returns another function it’s also called a higher order function.
function greet(message) {
return function(name) {
console.log(message, name);
};
}
const hello = greet('Hello');
console.log(hello('Mark')); // Hello Mark
Here, instead of creating a separate variable to store the result of greet function, we can directly call it like this:
console.log(greet('Hello')('Mark')); // Hello Mark
Every function we write has access to the arguments object which contains the list of values passed while calling the function:
function add() {
let sum = 0;
for(let i = 0; i < arguments.length; i++) {
sum += arguments[i];
}
console.log(sum); // 15
}
add(1, 2, 3, 4, 5);
Note: arrow functions do not have access to the arguments object.
So using this higher order function and arguments object, we can implement the product method in the following two ways.
function product(a) {
if (arguments.length == 2) {
return arguments[0] * arguments[1];
} else {
return function(b) {
return a * b;
};
}
}
console.log(product(4, 5)); // 20
console.log(product(4)(5)); // 20
function product(a, b) {
if (b) { // if b exists
return a * b;
} else {
return function(b) {
return a * b;
};
}
}
console.log(product(4, 5)); // 20
console.log(product(4)(5)); // 20
There is one issue in the second approach. In javascript, 0 is considered as a falsy value.
So we get different output if we call the function as shown below:
console.log(product(4, 0)); // function (b) {}
console.log(product(4)(0)); // 0
So to fix that, we can re-write the above function as
function product(a, b) {
if (b || b === 0) { // if b exists or b is zero
return a * b;
} else {
return function(b) {
return a * b;
};
}
}
console.log(product(4, 0)); // 0
console.log(product(4)(0)); // 0
console.log(product(4, 5)); // 20
console.log(product(4)(5)); // 20
You can add extra validation also inside the function to check if the values passed to function are numbers and only then return product else return some generic error message like “input is not valid”
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