_.array.selectors.js.md

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_.array.selectors.js.md
¶

array.selectors

Functions to take things from arrays. View Annotated Source

second

The _.second function is a convenience for the equivalent array[1]:
```
_.second(['a','b']);
```

¶

=> 'b'

_.map([['a','b'], _.range(10,20)], _.second);

¶

=> ['b',11]

You can also pass an optional number to the _.second function to take a number of elements from an array starting with the second element and ending at the given index:
```
_.second(_.range(10), 5)
```
¶

=> [1, 2, 3, 4]

third

The _.third function is a convenience for the equivalent array[2]:
```
_.third(['a','b','c']);
```

¶

=> 'c'

_.map([['a','b','c'], _.range(10,20)], _.third);

¶

=> ['c',12]

You can also pass an optional number to the _.third function to take a number of elements from an array starting with the third element and ending at the given index:
```
_.third(_.range(10), 5)
```
¶

=> [2, 3, 4]

nth

The _.nth function is a convenience for the equivalent array[n]:
```
_.nth(['a','b','c'], 2);
```
¶

=> 'c'

If given an index out of bounds then _.nth will return undefined:
```
_.nth(['a','b','c'], 2000);
```
¶

=> undefined

The _.nth function can also be used in conjunction with _.map and _.compact like so:
```
var b = [['a'],['b'],[]];

_.compact(_.map(b, function(e) { return _.nth(e,0) }));
```
¶

=> ['a','b']

If wrapping a function around _.nth is too tedious or you'd like to partially apply the index then lodash-contrib offers any of _.flip2, _.fix or rcurry2 to solve this.

takeWhile

The _.takeWhile function takes an array and a function and returns a new array containing the first n elements in the original array for which the given function returns a truthy value:
```
var isNeg = function(n) { return n < 0; };

_.takeWhile([-2,-1,0,1,2], isNeg);
```
¶

=> [-2,-1]

dropWhile

The _.dropWhile function works similarly except that it drops elements from the original array for which the given function returns a truthy value:
```
_.dropWhile([-2,-1,0,1,2], isNeg);
```
¶

=> [0,1,2]