你並不須要Underscore/Lodash

You don't (may not) need Lodash/Underscore

Lodash 和 Underscore 是很是優秀的當代JavaScript的工具集合框架，它們被前端開發者普遍地使用。可是，當咱們如今是針對現代化瀏覽器進行開發時，不少時候咱們利用的Underscore中的方法已經被ES5與ES6所支持了，若是咱們但願咱們的項目儘量地減小依賴的話，咱們能夠根據目標瀏覽器來選擇不用Lodash或者Underscore。

開發者的聲音

Make use of native JavaScript object and array utilities before going big.
Cody lindley, Author of jQuery Cookbook,JavaScript Enlightenment

You probably don't need Lodash. Nice List of JavaScript methods which you can use natively.
Daniel Lamb, Computer Scientist, Technical Reviewer of Secrets of the JavaScript Ninja, Functional Programming in JavaScript

I guess not, but I want it.
Tero Parviainen, Author of build-your-own-angular

I'll admit, I've been guilty of overusing #lodash. Excellent resource.
therebelrobot, Maker of web things, Facilitator for Node.js/io.js

Quick links

1. _.each

2. _.map

3. _.every

4. _.some

5. _.reduce

6. _.reduceRight

7. _.filter

8. _.find

9. _.findIndex

10. _.indexOf

11. _.lastIndexOf

12. _.includes

13. _.keys

14. _.size

15. _.isNaN

16. _.reverse

17. _.join

18. _.toUpper

19. _.toLower

20. _.trim

21. _.repeat

22. _.after

_.each

遍歷一系列的元素，而且調用回調處理方程。
Iterates over a list of elements, yielding each in turn to an iteratee function.

// Underscore/Lodash
_.each([1, 2, 3], function(value, index) {
  console.log(value);
});
// output: 1 2 3

// Native
[1, 2, 3].forEach(function(value, index) {
  console.log(value);
});
// output: 1 2 3

Browser Support

✔	1.5 ✔	9 ✔	✔	✔

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_.map

將某個列表中的元素映射到新的列表中。

// Underscore/Lodash
var array1 = [1, 2, 3];
var array2 = _.map(array1, function(value, index) {
  return value*2;
});
console.log(array2);
// output: [2, 4, 6]

// Native
var array1 = [1, 2, 3];
var array2 = array1.map(function(value, index) {
  return value*2;
});
console.log(array2);
// output: [2, 4, 6]

Browser Support

✔	1.5 ✔	9 ✔	✔	✔

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_.every

測試數組的全部元素是否都經過了指定函數的測試。

// Underscore/Lodash
function isLargerThanTen(element, index, array) {
  return element >=10;
}
var array = [10, 20, 30];
var result = _.every(array, isLargerThanTen);
console.log(result);
// output: true

// Native
function isLargerThanTen(element, index, array) {
  return element >=10;
}

var array = [10, 20, 30];
var result = array.every(isLargerThanTen);
console.log(result);
// output: true

Browser Support

✔	1.5 ✔	9 ✔	✔	✔

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_.some

判斷序列中是否存在元素知足給定方程的條件。

// Underscore/Lodash
function isLargerThanTen(element, index, array) {
  return element >=10;
}
var array = [10, 9, 8];
var result = _.some(array, isLargerThanTen);
console.log(result);
// output: true

// Native
function isLargerThanTen(element, index, array) {
  return element >=10;
}

var array = [10, 9, 8];
var result = array.some(isLargerThanTen);
console.log(result);
// output: true

Browser Support

✔	1.5 ✔	9 ✔	✔	✔

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_.reduce

接收一個函數做爲累加器（accumulator），數組中的每一個值（從左到右）開始縮減，最終爲一個值。

// Underscore/Lodash
var array = [0, 1, 2, 3, 4];
var result = _.reduce(array, function (previousValue, currentValue, currentIndex, array) {
  return previousValue + currentValue;
});
console.log(result);
// output: 10

// Native
var array = [0, 1, 2, 3, 4];
var result = array.reduce(function (previousValue, currentValue, currentIndex, array) {
  return previousValue + currentValue;
});
console.log(result);
// output: 10

Browser Support

✔	3.0 ✔	9 ✔	10.5	4.0

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_.reduceRight

接受一個函數做爲累加器（accumulator），讓每一個值（從右到左，亦即從尾到頭）縮減爲一個值。（與 reduce() 的執行方向相反）

// Underscore/Lodash
var array = [0, 1, 2, 3, 4];
var result = _.reduceRight(array, function (previousValue, currentValue, currentIndex, array) {
  return previousValue - currentValue;
});
console.log(result);
// output: -2

// Native
var array = [0, 1, 2, 3, 4];
var result = array.reduceRight(function (previousValue, currentValue, currentIndex, array) {
  return previousValue - currentValue;
});
console.log(result);
// output: -2

Browser Support

✔	3.0 ✔	9 ✔	10.5	4.0

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_.filter

使用指定的函數測試全部元素，並建立一個包含全部經過測試的元素的新數組。

// Underscore/Lodash
function isBigEnough(value) {
  return value >= 10;
} 
var array = [12, 5, 8, 130, 44];
var filtered = _.filter(array, isBigEnough);
console.log(filtered);
// output: [12, 130, 44]

// Native
function isBigEnough(value) {
  return value >= 10;
} 
var array = [12, 5, 8, 130, 44];
var filtered = array.filter(isBigEnough);
console.log(filtered);
// output: [12, 130, 44]

Browser Support

✔	1.5 ✔	9 ✔	✔	✔

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_.find

返回數組中知足測試條件的一個元素，若是沒有知足條件的元素，則返回 undefined。

// Underscore/Lodash
var users = [
  { 'user': 'barney',  'age': 36, 'active': true },
  { 'user': 'fred',    'age': 40, 'active': false },
  { 'user': 'pebbles', 'age': 1,  'active': true }
];

_.find(users, function(o) { return o.age < 40; });
// output: object for 'barney'

// Native
var users = [
  { 'user': 'barney',  'age': 36, 'active': true },
  { 'user': 'fred',    'age': 40, 'active': false },
  { 'user': 'pebbles', 'age': 1,  'active': true }
];

users.find(function(o) { return o.age < 40; });
// output: object for 'barney'

Browser Support

45.0	25.0 ✔	Not supported	Not supported	7.1

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_.findIndex

用來查找數組中某指定元素的索引, 若是找不到指定的元素, 則返回 -1.

// Underscore/Lodash
var users = [
  { 'user': 'barney',  'age': 36, 'active': true },
  { 'user': 'fred',    'age': 40, 'active': false },
  { 'user': 'pebbles', 'age': 1,  'active': true }
];

var index =  _.findIndex(users, function(o) { return o.age >= 40; });
console.log(index);
// output: 1

// Native
var users = [
  { 'user': 'barney',  'age': 36, 'active': true },
  { 'user': 'fred',    'age': 40, 'active': false },
  { 'user': 'pebbles', 'age': 1,  'active': true }
];

var index =  users.findIndex(function(o) { return o.age >= 40; });
console.log(index);
// output: 1

Browser Support

45.0	25.0 ✔	Not supported	Not supported	7.1

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_.indexOf

返回指定值在字符串對象中首次出現的位置。從 fromIndex 位置開始查找，若是不存在，則返回 -1。

// Underscore/Lodash
var array = [2, 9, 9];
var result = _.indexOf(array, 2);    
console.log(result); 
// output: 0

// Native
var array = [2, 9, 9];
var result = array.indexOf(2);    
console.log(result); 
// output: 0

Browser Support

✔	1.5 ✔	9 ✔	✔	✔

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_.lastIndexOf

返回指定元素（也即有效的 JavaScript 值或變量）在數組中的最後一個的索引，若是不存在則返回 -1。從數組的後面向前查找，從 fromIndex 處開始。

// Underscore/Lodash
var array = [2, 9, 9, 4, 3, 6];
var result = _.lastIndexOf(array, 9);    
console.log(result); 
// output: 2

// Native
var array = [2, 9, 9, 4, 3, 6];
var result = array.lastIndexOf(9);    
console.log(result); 
// output: 2

Browser Support

✔	✔	9 ✔	✔	✔

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_.includes

判斷元素是否在列表中

var array = [1, 2, 3];
// Underscore/Lodash - also called with _.contains
_.includes(array, 1);
// → true

// Native
var array = [1, 2, 3];
array.includes(1);
// → true

Browser Support

47✔	43 ✔	Not supported	34	9

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_.keys

返回某個對象全部可枚舉的鍵名。

// Underscore/Lodash 
var result = _.keys({one: 1, two: 2, three: 3});
console.log(result);
// output: ["one", "two", "three"]

// Native
var result2 = Object.keys({one: 1, two: 2, three: 3});
console.log(result2); 
// output: ["one", "two", "three"]

Browser Support

5✔	4.0 ✔	9	12	5

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_.size

返回集合大小。

// Underscore/Lodash
var result = _.size({one: 1, two: 2, three: 3});
console.log(result);
// output: 3

// Native
var result2 = Object.keys({one: 1, two: 2, three: 3}).length;
console.log(result2); 
// output: 3

Browser Support

5✔	4.0 ✔	9	12	5

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_.isNaN

判斷是否爲NaN

// Underscore/Lodash
console.log(_.isNaN(NaN));
// output: true

// Native
console.log(isNaN(NaN));
// output: true

// ES6
console.log(Number.isNaN(NaN));
// output: true

MDN:

In comparison to the global isNaN() function, Number.isNaN() doesn't suffer the problem of forcefully converting the parameter to a number. This means it is now safe to pass values that would normally convert to NaN, but aren't actually the same value as NaN. This also means that only values of the type number, that are also NaN, return true. Number.isNaN()

Voice from the Lodash author:

Lodash's _.isNaN is equiv to ES6 Number.isNaN which is different than the global isNaN.
--- jdalton

Browser Support for isNaN

✔	✔	✔	✔	✔

Browser Support for Number.isNaN

25	15	Not supported	✔	9

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_.reverse

Lodash only
將一個序列反向。

// Lodash
var array = [1, 2, 3];
console.log(_.reverse(array));
// output: [3, 2, 1]

// Native
var array = [1, 2, 3];
console.log(array.reverse());
// output: [3, 2, 1]

Voice from the Lodash author:

Lodash's _.reverse just calls Array#reverse and enables composition like _.map(arrays, _.reverse).

It's exposed on _ because previously, like Underscore, it was only exposed in the chaining syntax.

--- jdalton

Browser Support

1.0✔	1.0✔	5.5✔	✔	✔

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_.join

Lodash only
將一個序列變成一個字符串。

// Lodash
var result = _.join(['one', 'two', 'three'], '--');
console.log(result);
// output: 'one--two--three'

// Native
var result = ['one', 'two', 'three'].join('--');
console.log(result)
// output: 'one--two--three'

Browser Support

1.0✔	1.0✔	5.5✔	✔	✔

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_.toUpper

Lodash only
將字符串大寫。

// Lodash
var result = _.toUpper('foobar');
console.log(result);
// output: 'FOOBAR'

// Native
var result = 'foobar'.toUpperCase();
console.log(result);
// output: 'FOOBAR'

Browser Support

✔	✔	✔	✔	✔

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_.toLower

Lodash only
將字符串變爲小寫。

// Lodash
var result = _.toLower('FOOBAR');
console.log(result);
// output: 'foobar'

// Native
var result = 'FOOBAR'.toLowerCase();
console.log(result);
// output: 'foobar'

Browser Support

✔	✔	✔	✔	✔

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_.trim

Lodash only
消去字符串起始的空白。

// Lodash
var result = _.trim(' abc ');
console.log(result);
// output: 'abc'

// Native
var result = ' abc '.trim();
console.log(result);
// output: 'abc'

Browser Support

5.0✔	3.5✔	9.0✔	10.5✔	5.0✔

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_.repeat

Lodash only
重複建立字符串。

// Lodash
var result = _.repeat('abc', 2);
// output: 'abcabc'

// Native
var result = 'abc'.repeat(2);
console.log(result);
// output: 'abcabc'

Browser Support

41✔	24✔	Not supported	Not supported	9

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_.after

Note this is an alternative implementation
建立一個在通過了指定計數器以後纔會被調用的方程。

var notes = ['profile', 'settings'];
// Underscore/Lodash
var renderNotes = _.after(notes.length, render);
   notes.forEach(function(note) {
   console.log(note);
   renderNotes();
});

 // Native
notes.forEach(function(note, index) {
 console.log(note);
 if (notes.length === (index + 1)) {
   render();
 }
});

Browser Support

✔	✔	✔	✔	✔

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Reference

• Mozilla Developer Network

• Underscore.js

• Lodash.js

Inspired by:

• You-Dont-Need-jQuery

• Rui's blog