This is a script to be used together with Phantomjs to automatically login to CHT wifi access-points.

wifi-login.js

var url = 'http://captive.apple.com/';
var fs = require('fs');
var file = fs.open('credential', 'r');
var credentials = file.read().split('\n');
file.close();

// How often (in milliseconds) the program should check the login status.
var checkInterval = 5000;
// How long (in millisecond) should be program wait after the submit button
// on the login form is pressed before closing the page object.
var waitTimeout = 5000;
// Config object with the credentials that is necessary to login to the
// wifi acess-point.
var loginConfig = {
    loginType: 2,
    username: credentials[0],
    passwd: credentials[1]
}

// Regular expressions used to check what webpage is currently displayed in the
// page object.
var loginUrl = new RegExp('https:\\/\\/authweb.hinet.net\\/auth\\/auth_login');
var successUrl = new RegExp('http:\\/\\/authweb.hinet.net\\/auth\\/auth_success');

function fillCredential (page) {
    page.evaluate(function (config) {
        seltype(config.loginType);
        var optionIndex = config.loginType - 1;
        var inputUsername = document.getElementsByName('cht_user')[optionIndex];
        var inputPasswd = document.getElementsByName('passwd')[optionIndex];
        inputUsername.value = config.username;
        inputPasswd.value = config.passwd;
        document.getElementById('submit').click();
    }, loginConfig);
    console.log('Submit button clicked...');
};

function checkStatus (status) {
    // Unless there is a problem with the Wifi connection, the status should
    // alway be 'success'.
    if (status !== 'success') {
        console.log('Something is wrong with the wifi connection!');
    }
};

function login() {
    var page = require('webpage').create();
    var timerId = 0;
    // Since the browser is redirected to the login page, using callback from
    // `page.on` won't work, as the callback will be fired before arriving at
    // the page with the login form.
    // We need to rely on `page.onLoadFinished` to check the page's url and
    // determine what to do next.
    page.onLoadFinished = function() {
        // If the current page is the one with login form, then fill in the
        // credentials and click the submit button.
        if (page.url.match(loginUrl)) {
            console.log('Filling the credentials...');
            fillCredential(page);
            // Close the page object after the `waitTimeout` millisecond.
            // This servers two purpose, first it keeps a reference to the
            // page object so it won't be GCed (which is the most import
            // reason), second it make sure the page object is closed to
            // release the memory.
            timerId = setTimeout(function() {
                page.close();
            }, waitTimeout);
        // If the current page is one of the successful page (meaning login
        // has succeed), print a success message and close the page object.
        } else if (page.url.match(successUrl) || page.url === url) {
            clearTimeout(timerId);
            console.log('Login Success, now at ' + page.url);
            page.close();
        } else {
            console.log('Currently at ' + page.url);
        }
    }
    page.open(url, checkStatus);
} 

// Check the login status at an interval, and login if necessary.
setInterval(login, checkInterval);