The underscore learning array

Array Functions

1._first ([], N), _last ([], N), _initial ([], N)

_.first ([], N): takes the first n elements into an array to return, no N, and defaults back to the initial option (non-array)

_.first ([' A ', ' B ', ' C '])//n, take the first element
	"a"

_.first ([' A ', ' B ', ' C '],1)//plus n, take an array of the first n elements
	["a"]

_.first ([' A ', ' B ', ' C '],2)
	["A", "B"]

_.last ([], N): After taking an array of n elements to return, no N, the default is to return the last option (non-array);

_initial ([], N): Takes out an array that does not contain the last item;

2._.rest ([], N): Returns an array from N, N: default = 1, which does not contain the first item

_.rest ([' A ', ' B ', ' C ', ' d '],2)
	[' C ', ' d ']

_.rest ([' A ', ' B ', ' C ', ' d '])
	[' B ', ' C ', ' d ']

3._.compact ([]): Remove false value in array (null,undefined,nan,0, ')

_.compact ([0, 1, False, 2, ', 3]);
= = [1, 2, 3]

4._.flatten ([], level): Converts multiple, multidimensional arrays into an array, levels control hierarchy

All flattening

_.flatten ([1, [2], [3, [[4]]]);
= = [1, 2, 3, 4];

Flatten only the first dimensional array

_.flatten ([1, [2], [3, [[4]]]], true);
= = [1, 2, 3, [[4]]];

5. _. Union ([],[],[],...): Set

_.intersection ([],[],[],...) : Intersection

_.diffrence ([],[],[],...) : Difference Set

_.without ([],arg1,arg2): Difference set exclusion

_.uniq ([]): Array de-weight

6._.zip ([],[],[]), _unzip ([],[],[])

_.zip ([' Moe ', ' Larry ', ' Curly '], [+, +], [True, False, false]);
= = [["Moe", +, True], ["Larry", +, false], ["Curly", "false]]

_.unzip ([["Moe", +, True], ["Larry", "Max," false], ["Curly", []]);
= = [' Moe ', ' Larry ', ' Curly '], [[+, +], [True, False, false]]

7._.object ([],[]) array variable object JSON

_.object ([' Moe ', ' Larry ', ' Curly '], [+, +]);
= = {moe:30, larry:40, curly:50} _.object ([' Moe ', ' +], ['
Larry ', ' +], [' Curly ', ']]);
= = {moe:30, larry:40, curly:50}

8._.range (start:0,stop,step); Creates an array of step for start to stop

_.range (ten);
= = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
_.range (1, one);
= = [1, 2, 3, 4, 5, 6, 7, 8, 9, ten]
_.range (0,, 5);
= = [0, 5, ten, +,
0, -10,-1] _.range;
= = [0,-1,-2, -3, -4, -5,-6,-7,-8,-9]
_.range (0);
= []