phantomjs的domready事件实现

phantomjs原生只有onload事件，而没有domready事件的实现。以下是自己的实现：

const PHANTOM_FUNCTION_PREFIX = '/* PHANTOM_FUNCTION */';

var page = require('webpage').create();

page.onConsoleMessage = function(msg) {
    if (msg.indexOf("PHANTOM_FUNCTION") === 0) {
    page.onDOMContentLoaded();
    } else {
    console.log(msg);
    }
};

page.onInitialized = function() {
    page.evaluate(function(domContentLoadedMsg) {
    document.addEventListener('DOMContentLoaded', function() {
        console.log("PHANTOM_FUNCTION");
    }, false);
    }, "PHANTOM_FUNCTION");
};

page.onDOMContentLoaded = function() {
    // your code here
    console.log('DOMContentLoaded');
};