有时候还是用油猴方便，WebDriver考虑的太多
//获取元素，一直查询，直到找到为止，参数名称比较好理解
function getElement(parent, selector, timeout = 0) {
return new Promise(resolve => {
let result = parent.querySelector(selector);
if (result) return resolve(result);
let timer;
const mutationObserver = window.MutationObserver || window.WebkitMutationObserver || window.MozMutationObserver;
if (mutationObserver) {
const observer = new mutationObserver(mutations => {
for (let mutation of mutations) {
for (let addedNode of mutation.addedNodes) {
if (addedNode instanceof Element) {
result = addedNode.matches(selector) ? addedNode : addedNode.querySelector(selector);
if (result) {
observer.disconnect();
timer && clearTimeout(timer);
return resolve(result);
}
}
}
}
});
observer.observe(parent, {
childList: true,
subtree: true
});
if (timeout > 0) {
timer = setTimeout(() => {
observer.disconnect();
return resolve(null);
}, timeout);
}
} else {
const listener = e => {
if (e.target instanceof Element) {
result = e.target.matches(selector) ? e.target : e.target.querySelector(selector);
if (result) {
parent.removeEventListener('DOMNodeInserted', listener, true);
timer && clearTimeout(timer);
return resolve(result);
}
}
};
parent.addEventListener('DOMNodeInserted', listener, true);
if (timeout > 0) {
timer = setTimeout(() => {
parent.removeEventListener('DOMNodeInserted', listener, true);
return resolve(null);
}, timeout);
}
}
});
}//劫持XHR，懂得都懂
function addXMLRequestCallback(callback){
//是一个劫持的函数
var oldSend, i;
if( XMLHttpRequest.callbacks ) {
//判断XMLHttpRequest对象下是否存在回调列表，存在就push一个回调的函数
// we've already overridden send() so just add the callback
XMLHttpRequest.callbacks.push( callback );
} else {
// create a callback queue
XMLHttpRequest.callbacks = [callback];
//如果不存在则在xmlhttprequest函数下创建一个回调列表
// store the native send()
oldSend = XMLHttpRequest.prototype.send;
//获取旧xml的send函数，并对其进行劫持
// override the native send()
XMLHttpRequest.prototype.send = function(){
// process the callback queue
// the xhr instance is passed into each callback but seems pretty useless
// you can't tell what its destination is or call abort() without an error
// so only really good for logging that a request has happened
// I could be wrong, I hope so...
// EDIT: I suppose you could override the onreadystatechange handler though
for( i = 0; i < XMLHttpRequest.callbacks.length; i++ ) {
XMLHttpRequest.callbacks[i]( this );
}
//循环回调xml内的回调函数
// call the native send()
oldSend.apply(this, arguments);
//由于我们获取了send函数的引用，并且复写了send函数，这样我们在调用原send的函数的时候，需要对其传入引用，而arguments是传入的参数
}
}
}
//使用范例
/*
addXMLRequestCallback( function( xhr ) {
//调用劫持函数，填入一个function的回调函数
//回调函数监听了对xhr调用了监听load状态，并且在触发的时候再次调用一个function，进行一些数据的劫持以及修改
xhr.addEventListener("load", function(){
if ( xhr.readyState == 4 && xhr.status == 200 ) {
//console.log( xhr.responseURL );
//your code
//console.log(xhr.responseText);
}
});
});
*/
