Lodash notes.

gistfile1.md

Lodash

1. _() vs _.chain()

> _([1,2,3,4,5]).map(function (x) { return x * x }).first(3).value()
[ 1, 4, 9 ] // the same if first(3)
> _.chain([1,2,3,4,5]).map(function (x) { return x * x }).first(3).value()
[ 1, 4, 9 ] // the same if first(3)
> _.chain([1,2,3,4,5]).map(function (x) { return x * x }).first()
{ __chain__: true, __wrapped__: 1 } // still a chain.
> _([1,2,3,4,5]).map(function (x) { return x * x }).first()
1 // without param to first, it returns the value directly if _() #weird?

Prefer _.chain()

2. Don't _.chain everything

http://jsperf.com/lodash-chain

Chain is 65% slower.

3. Prefer _.each instead of native ForEach

_.each is faster because it does less checks, supports sparse array differently.

http://jsfiddle.net/BhrT3/

4. function context is optional in most methods.

Instead of _.map(array, module.function.bind(module))

Do _.map(array, module.function, module)

e.g _.map(keys, model.get, model)

5. _.pick, _.omit and _.transform

_.pick({ 'name': 'fred', '_userid': 'fred1' }, 'name');
// → { 'name': 'fred' }
_.omit({ 'name': 'fred', '_userid': 'fred1' }, '_userid');
// → { 'name': 'fred' }

_.transform

var mapped = _.transform({ 'name': 'fred', '_userid': 'fred1' }, function(result, val, key) {
  if (key === 'name') {
     result[key] = val.toUpperCase();
  }
});
// → { 'name': 'FRED' }

6. _.noop , don't do function () {}

7. _.merge vs _.extend

_.merge concats. _.extend replaces.

var names = {
  'characters': [
    { 'name': 'barney' },
    { 'name': 'fred' }
  ]
};

var ages = {
  'characters': [
    { 'age': 36 },
    { 'age': 40 }
  ]
};

_.merge(names, ages);
// → { 'characters': [{ 'name': 'barney', 'age': 36 }, { 'name': 'fred', 'age': 40 }] }
_.extend(names, ages);
// → { 'characters': [{ 'age': 36 }, { 'age': 40 }] }

_.defaults

var customOptions = { 'mysql': { 'host': 'prod.mysql.host' } }
  , defaultOptions = { mysql: { 'host': 'localhost', port: '1234'} , redis: true }

_.defaults(customOptions, defaultOptions);
// → {mysql: { 'host': 'prod.mysql.host' }, redis: true}

// Mutates destination object!
customOptions 
// → {mysql: { 'host': 'prod.mysql.host' }, redis: true}

_.defaults({}, customOptions, defaultOptions);

_.merge({}, customOptions, defaultOptions);
// → { mysql: { 'host': 'prod.mysql.host', port: '1234'} , redis: true }

8. _.any and _.all

.any (.some) .all (.every)

_.any([null, '', undefined, 'something'])
// => true
_.all(['something', 0, true])
// => false
_.all(['something', 'another', true])
// => true

9. _.curry vs _.partial

var logABC = function(a, b, c) {
  console.log(a + b + c);
}

var curried = _.curry(logABC);

curried(1)(2)(3);
// → 6

function asyncGet(id, joiner, callback) {
   request(id, function (response) {
     callback(response.body, joiner)
   }
}

asyncGet('a', curried, function (a, joiner) { 
  asyncGet('b', joiner(a), function (b, joiner) {
    asyncGet('c', joiner(b), function (c, joiner) {
       joiner(c)
    })
  })
})

// _.partial
asyncGet('a', logABC, function (a, joiner) { 
  asyncGet('b', _.partial(joiner, a), function (b, joiner) {
    asyncGet('c', _.partial(joiner, b), function (c, joiner) {
       joiner(c)
    })
  })
})

_.partial

// instead of 
var func2 = obj.func.bind(obj, 'a', b')

// does not alter 'this' context
var func2 = _.partial(obj.func, 'a', 'b')

10. _.parseInt vs native parseInt

Avoids differences in native ES3 and ES5 parseInt implementations

ES5 removes octal interpretation. ES3 (IE versions 7 & 8)

_.parseInt('080') // 0

// pass in base 10.
_.parseInt('080', 10)

http://lodash.com/docs

---

_.template _.memoize _.wrap _.bindAll