Month: September 2017

Function currying

Given a function call sum(1)(2), write a function with currying and without currying.

With currying –

var sum = function(num1) {
  return function(num2) {
    return num1 + num2;
 }
}

Without currying, we can create a sum function on the prototype object of Function. Since we will be using apply function to provide argument to the sum function, we will have to convert ‘argument’ array(which is not actually an array) to array so that we would be able to use concat function to combine both the arguments(num1,num2).

So we write this toArray function as below.

var toArray = function(args) {
  Array.prototype.slice.call(args);
}

and we write sum function as below –

var sum = function(){
self = this;
var args = toArray(arguments);
 return function(){
  return self.apply(this, args.concat(toArray(arguments)))
 }
}

Using Object.assign

The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.

Ex.

var options = {animation: true; speed:'2s'};
var defaultOptions = {animation: false; speed: '2s'};
Object.assign(defaultOptions, options); // {animation: true, speed: "2s"};

We can merge multiple objects together using Object.assign.

var animation = {type: 'ease in', time: '2s'};
var size = {width:20, height:10};
var sprite = Object.assign(animation,size); //{type: "ease in", time: "2s", width: 20, height: 10}