I had an apps to use phantomjs to generate a report by using Google Charts.

The apps will spawn a child process to execute phantomjs command, to load a web page that contains the charts, and then take a screenshots saving into JPG, which later convert into PDF for archive.

In the code, it needs to load the following JS URL from Google: https://www.google.com/jsapi, which is HTTPS based.

Suddenly it is stopped working since last month.

By checking the log and found that PhantomJS encountered JavaScript error: “ReferenceError, can’t find Google”. Hey, I tried to open the web page in my local Chrome browser, and it still working. I tried to CuRL from my server, still can download the page. So I suspected might be SSL issues on PhantomJS.

Tried googling and found a solution. As Google had already deprecated the old version of SSL (SSLv3) and use TLSv1.

In the command line, we need to add one more option: –ssl-protocol=tlsv1, to bypass the HTTPS error, and it turns out it is working now.


phantomjs --ssl-protocol=tlsv1 your-code.js


I came across this stun.js code and found one interesting implementation of inet_aton functions. I curious of its formula and equation.

function inet_aton(a) {
    var d = a.split('.');
    return ((((((+d[0])*256)+(+d[1]))*256)+(+d[2]))*256)+(+d[3]);
}

I written a simple Node.JS test script just to evaluate, calculate different implementations of inet_aton, and here is my findings:

function inet_aton(a) {
    var d = a.split('.');
    return ((((((+d[0])*256)+(+d[1]))*256)+(+d[2]))*256)+(+d[3]);
}
function inet_aton_b(ip){
    var a = new Array();
    a = ip.split('.');
    return((a[0] < < 24) >>> 0)  + ((a[1] < < 16) >>> 0) + ((a[2] < < 8) >>> 0) + (a[3] >>> 0);
}

function inet_aton_c(a) {
   var d = a.split('.');
   return d[0] * 256 * 256 * 256 + d[1] * 256 * 256 + d[2] * 256 + d[3];
}

var start;
start = new Date().getTime();
for(var i = 0; i < 1000000; i++) {
inet_aton('1.1.1.1')
}
console.log('elapsed:' + (new Date().getTime() - start));


start = new Date().getTime();
for(var i = 0; i < 1000000; i++) {
inet_aton_b('1.1.1.1')
}
console.log('elapsed:' + (new Date().getTime() - start));

start = new Date().getTime();
for(var i = 0; i < 1000000; i++) {
inet_aton_c('1.1.1.1')
}
console.log('elapsed:' + (new Date().getTime() - start));

See the first implementation run faster. The key point is lesser multiplication is performed, by factoring using simple math.

I run the same code on Java but I found different things, I can't tell which one run faster than other one. If I run the first code first, second code followed, always the second block faster than first block. If I exchange, run second code first, first code followed, always the second block faster than first block. They both run in same speed. I even use javap to view its bytecode and found second code have more instruction than first one, but might be JVM can do its optimization so that end result both code run same speed.

This is JavaScript Tips on Objects and Array and their For loop.

In JavaScript, there is an Object and represented as:


var someObj = {name:"YongHao", age:25}


There is an Array and represented as:


var someArr = [1,2,3,4]


Use normal for loop only for Array, and use for…in only for Object.

For example, for Object

var someObj = {name:"YongHao", age:25}
for(var i in someObj) {
  console.log(i + ' - ' + someObj[i]);
}

We get:
name – YongHao
age – 25

For Array

var someArr = [1,2,3,4]
for(var i = 0; i < someArr.length; i++) {
  console.log(i + ' - ' + someArr[i]);
}

We get:
0 - 1
1 - 2
2 - 3
3 - 4

Do not use for...in to Array, if you do:

var someArr = [1,2,3,4]
for(var i in someArr) {
  console.log(i + ' - ' + someArr[i]);
}

It may return good result, but not recommended, as i now is a string but not an integer.