到現在為止,已經大半了.感覺這個_還是蠻基礎(不是簡單)的,基本上把函數語言程式設計發揮的很盡興,除了pluck本人不是很喜歡外,不過當成select算了.多記個單詞.
接下來是Array,其實這裡不得不說下,JS的Array的物件,Json有點糾纏不清,這就是廣義相對論,離大統一場論只差一步啊.
這裡同時不得不提到一下,函數語言程式設計的真諦,正在逐步浮出,我們發現函式式往往是一個集合,附加上一個操作,或者說是一種規則.當然還有一個可選環境,這就是函式式的世界啊.
Array Functions
Note: All array functions will also work on the arguments object. However, Underscore functions are not designed to work on "sparse" arrays.
first_.first(array, [n]) Alias: head, take
Returns the first element of an array. Passing n will return the first n elements of the array.
_.first([5, 4, 3, 2, 1]); => 5
initial_.initial(array, [n])
Returns everything but the last entry of the array. Especially useful on the arguments object. Pass n to exclude the last n elements from the result.
_.initial([5, 4, 3, 2, 1]); => [5, 4, 3, 2]
last_.last(array, [n])
Returns the last element of an array. Passing n will return the last n elements of the array.
_.last([5, 4, 3, 2, 1]); => 1
rest_.rest(array, [index]) Alias: tail, drop
Returns the rest of the elements in an array. Pass an index to return the values of the array from that index onward.
_.rest([5, 4, 3, 2, 1]); => [4, 3, 2, 1]
compact_.compact(array)
Returns a copy of the array with all falsy values removed. In JavaScript, false, null, 0,"", undefined and NaN are all falsy.
_.compact([0, 1, false, 2, '', 3]); => [1, 2, 3]
flatten_.flatten(array, [shallow])
Flattens a nested array (the nesting can be to any depth). If you pass shallow, the array will only be flattened a single level.
_.flatten([1, [2], [3, [[4]]]]); => [1, 2, 3, 4]; _.flatten([1, [2], [3, [[4]]]], true); => [1, 2, 3, [[4]]];
without_.without(array, [*values])
Returns a copy of the array with all instances of the values removed.
_.without([1, 2, 1, 0, 3, 1, 4], 0, 1); => [2, 3, 4]
union_.union(*arrays)
Computes the union of the passed-in arrays: the list of unique items, in order, that are present in one or more of the arrays.
_.union([1, 2, 3], [101, 2, 1, 10], [2, 1]); => [1, 2, 3, 101, 10]
intersection_.intersection(*arrays)
Computes the list of values that are the intersection of all the arrays. Each value in the result is present in each of the arrays.
_.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]); => [1, 2]
difference_.difference(array, *others)
Similar to without, but returns the values from array that are not present in the otherarrays.
_.difference([1, 2, 3, 4, 5], [5, 2, 10]); => [1, 3, 4]
uniq_.uniq(array, [isSorted], [iterator]) Alias: unique
Produces a duplicate-free version of the array, using === to test object equality. If you know in advance that the array is sorted, passing true for isSorted will run a much faster algorithm. If you want to compute unique items based on a transformation, pass an iterator function.
_.uniq([1, 2, 1, 3, 1, 4]); => [1, 2, 3, 4]
zip_.zip(*arrays)
Merges together the values of each of the arrays with the values at the corresponding position. Useful when you have separate data sources that are coordinated through matching array indexes. If you're working with a matrix of nested arrays, zip.apply can transpose the matrix in a similar fashion.
_.zip(['moe', 'larry', 'curly'], [30, 40, 50], [true, false, false]); => [["moe", 30, true], ["larry", 40, false], ["curly", 50, false]]
object_.object(list, [values])
Converts arrays into objects. Pass either a single list of [key, value] pairs, or a list of keys, and a list of values.
_.object(['moe', 'larry', 'curly'], [30, 40, 50]);
=> {moe: 30, larry: 40, curly: 50}
_.object([['moe', 30], ['larry', 40], ['curly', 50]]);
=> {moe: 30, larry: 40, curly: 50}
目測可能常用
indexOf_.indexOf(array, value, [isSorted])
Returns the index at which value can be found in the array, or -1 if value is not present in the array. Uses the native indexOf function unless it's missing. If you're working with a large array, and you know that the array is already sorted, pass truefor isSorted to use a faster binary search ... or, pass a number as the third argument in order to look for the first matching value in the array after the given index.
_.indexOf([1, 2, 3], 2); => 1
目測可能常用
lastIndexOf_.lastIndexOf(array, value, [fromIndex])
Returns the index of the last occurrence of value in the array, or -1 if value is not present. Uses the native lastIndexOf function if possible. Pass fromIndex to start your search at a given index.
_.lastIndexOf([1, 2, 3, 1, 2, 3], 2); => 4
sortedIndex_.sortedIndex(list, value, [iterator], [context])
Uses a binary search to determine the index at which the value should be inserted into the list in order to maintain the list's sorted order. If an iterator is passed, it will be used to compute the sort ranking of each value, including the value you pass.
_.sortedIndex([10, 20, 30, 40, 50], 35); => 3
range_.range([start], stop, [step])
A function to create flexibly-numbered lists of integers, handy for each and map loops.start, if omitted, defaults to 0; step defaults to 1. Returns a list of integers from start tostop, incremented (or decremented) by step, exclusive.
_.range(10); => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] _.range(1, 11); => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] _.range(0, 30, 5); => [0, 5, 10, 15, 20, 25] _.range(0, -10, -1); => [0, -1, -2, -3, -4, -5, -6, -7, -8, -9] _.range(0); => []
目測可能常用
對於Array的這些擴充套件,目測實用性不太強,當然不排除對別人很有用.而且通過函式式使用Array,不如在Array上擴充套件,比如象Linq在enumable上的擴充套件,這樣子幹實用得多.也方便得多.