uuid.js

function uuid(){
    // https://github.com/GoogleChrome/chrome-platform-analytics/blob/master/src/internal/identifier.js
    const chars = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.split('');
    for(let i = 0, j = chars.length; i < j; i++){
        switch(chars[i]){
            case 'x':
                chars[i] = Math.floor(Math.random() * 16).toString(16);
                break;
            case 'y':
                chars[i] = (Math.floor(Math.random() * 4) + 8).toString(16);
                break;
        }
    }
    return chars.join('');
}