The power of Underscore.js

Underscore.js is a powerful JavaScript library that provides useful functional programming helpers. Why useful? Let see in a couple of examples below but in a few words it allows you to make your code more clear and compact.

First example is filtering of the list. Let say you have trivial list of integer numbers and need to find even ones. I am sure every developer knows how to do it using for loop:

var numbers = [1, 2, 3, 4, 5, 6];
var evens = [];
for (var i = 0; i < numbers.length; i++) {
  if (numbers[i] % 2 == 0) {
    evens.push(numbers[i]);
  }
}

Compare it with implementation using Underscore’s filter function:

var numbers = [1, 2, 3, 4, 5, 6];
var evens = _.filter(numbers, function(num) { 
  return num % 2 == 0; 
});

Second example is optimization of the search performed on some list. In some situation when you need to repeat array search in a cycle it make sense to convert it into hash map. Let’s say you have a list of integer numbers and you do as usual:

var numbers = [10, 11, 12, 25, 36];
var map = {};
for (var i = 0; i < numbers.length; i++) {
  map[numbers[i]] = numbers[i];
}

See how it’s trivial with indexBy function:

var numbers = [10, 11, 12, 25, 36];
var map = _.indexBy(numbers, function(n) { return n; });

So if you want to write less code to achive result, then Underscore.js is your friend :-) See Underscore.js web site and learn new useful tricks. Another good source of documentation for Undescore and many other libraries is DevDocs