Simple unique ids from no-so-unique values

example.js

var uniquify = require('uniquifier')();

console.log(uniquify(1));
// > "1"

console.log(uniquify(2));
// > "2"

console.log(uniquify(1));
// > "1_1"

console.log(uniquify(3));
// > "3"

console.log(uniquify(1));
// > "1_2"

console.log(uniquify(3));
// > "3_1"

uniquifier.js

module.exports = function uniquifier(delimiter) {
    var ids = {};
    
    delimiter = delimiter || '_';

    return function uniquify(value) {
        var id = String(value);
        
        if (ids[id] == null) {
            ids[id] = 0;

            return id;
        }

        ids[id]++;

        return id + delimiter + ids[id];      
    };
};