String performance test on Node -- index, slice, substring

JS-pt-string-index.slice.substring.js

var string = 'string',
    stringIndex = function () {
        string[0];
    },
    stringSlice = function () {
        string.slice(0, 1);
    },
    stringSubstring = function () {
        string.substring(0, 1);
    };

perfTest(stringIndex, 'String Index');
perfTest(stringSlice, 'String Slice');
perfTest(stringSubstring, 'String Substring');

function perfTest(fn, label) {
    var timer_start = process.hrtime(),
        timer_stop = process.hrtime;

    console.time(label);
    for (var i = 1e8; i--;) fn();
    console.timeEnd(label, timer_start - timer_stop());
}