[轉] 你並不需要Underscore/Lodash

[From] https://segmentfault.com/a/1190000004460234

 

Lodash 和 Underscore 是非常優秀的當代JavaScript的工具集合框架，它們被前端開發者廣泛地使用。但是，當我們現在是針對現代化瀏覽器進行開發時，很多時候我們利用的Underscore中的方法已經被ES5與ES6所支持了，如果我們希望我們的項目盡可能地減少依賴的話，我們可以根據目標瀏覽器來選擇不用Lodash或者Underscore。

 

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，並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

測試數組的所有元素是否都通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滿足給定方程的條件。

// 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

接收一個函數作為累加器（accumulator），數組中的每個值（從左到右）開始縮減，最終為一個值。

// 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

接受一個函數作為累加器（accumulator），讓每個值（從右到左，亦即從尾到頭）縮減為一個值。（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所有元素，並創建一個包含所有通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

返回數組中滿足測試條件的一個元素，如果沒有滿足條件的元素，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, 如果找不到指定的元素, 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，如果不存在，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）在數組中的最后一個的索引，如果不存在則返回 -1。從數組的后面向前查找，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

返回某個對象所有可枚舉的鍵名。

// 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

判斷是否為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
將字符串變為小寫。

// 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
重復創建字符串。

// 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
創建一個在經過了指定計數器之后才會被調用的方程。

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