Efficient Codes

EfficientCodes.txt

• Apply the array method map() to a string:
> [].map.call('abc', function (x) { return x.toUpperCase() })
[ 'A', 'B', 'C' ]

Using map() generically is more efficient than using split(''), which creates an intermediate array:
> 'abc'.split('').map(function (x) { return x.toUpperCase() })
[ 'A', 'B', 'C' ]

Apply a string method to nonstrings. toUpperCase() converts the receiver to a string and uppercases the result:
> String.prototype.toUpperCase.call(true)
'TRUE'
> String.prototype.toUpperCase.call(['a','b','c'])
'A,B,C'