24 lines
473 B
JavaScript
24 lines
473 B
JavaScript
|
var _ = require('underscore');
|
||
|
|
|
||
|
|
module.exports = {
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Get the next available letter.
|
||
|
|
* @param {Array} letters e.g. ['a', 'b', 'd']
|
||
|
|
* @return {String} e.g. 'c'
|
||
|
|
*/
|
||
|
|
next: function (letters) {
|
||
|
|
return _.chain(letters)
|
||
|
|
.sort()
|
||
|
|
.reduce(function (memo, letter) {
|
||
|
|
if (letter === memo) {
|
||
|
|
return String.fromCharCode(letter.charCodeAt() + 1);
|
||
|
|
} else {
|
||
|
|
return memo;
|
||
|
|
}
|
||
|
|
}, 'a')
|
||
|
|
.value();
|
||
|
|
}
|
||
|
|
|
||
|
|
};
|