gen_uid.js

// 还需要了解的：
//  - 什么是 UID
//  - 这四种方式优劣

function getId() {
    return "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx".replace(/x/g, function() {
        return Math.floor(Math.random()*16).toString(16).toUpperCase();
    });
}

function generateGuid() {
    var result, i, j;
    result = '';
    for(j=0; j<32; j++) {
        if( j == 8 || j == 12|| j == 16|| j == 20)
            result = result + '-';
        i = Math.floor(Math.random()*16).toString(16).toUpperCase();
        result = result + i;
    }
    return result;
}

// http://stackoverflow.com/questions/3242324/javascript-dateobj-gettime-for-a-uid-is-the-length-not-fixed
Math.random().toString(36).substr(2,9)

// http://stackoverflow.com/questions/6248666/how-to-generate-short-uid-like-ax4j9z-in-js
function generateUIDNotMoreThan1million() {
    return ("0000" + (Math.random()*Math.pow(36,4) << 0).toString(36)).substr(-4)
}

//================
function generateUUID(){
    var d = new Date().getTime();
    var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
        var r = (d + Math.random()*16)%16 | 0;
        d = Math.floor(d/16);
        return (c=='x' ? r : (r&0x7|0x8)).toString(16);
    });
    return uuid;
};

//=================
generateGUID = (typeof(window.crypto) != 'undefined' && 
                typeof(window.crypto.getRandomValues) != 'undefined') ?
    function() {
        // If we have a cryptographically secure PRNG, use that
        // http://stackoverflow.com/questions/6906916/collisions-when-generating-uuids-in-javascript
        var buf = new Uint16Array(8);
        window.crypto.getRandomValues(buf);
        var S4 = function(num) {
            var ret = num.toString(16);
            while(ret.length < 4){
                ret = "0"+ret;
            }
            return ret;
        };
        return (S4(buf[0])+S4(buf[1])+"-"+S4(buf[2])+"-"+S4(buf[3])+"-"+S4(buf[4])+"-"+S4(buf[5])+S4(buf[6])+S4(buf[7]));
    }

    :

    function() {
        // Otherwise, just use Math.random
        // http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript/2117523#2117523
        return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
            var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
            return v.toString(16);
        });
    };