maple3142/onbeforescriptexecute.js

## onbeforescriptexecute.js
// 'beforescriptexecute' event [es5]
// original version: https://gist.github.com/jspenguin2017/cd568a50128c71e515738413cd09a890

;(function() {
	;('use strict')
	function Event(script, target) {
		this.script = script
		this.target = target

		this._cancel = false
		this._replace = null
		this._stop = false
	}
	Event.prototype.preventDefault = function() {
		this._cancel = true
	}
	Event.prototype.stopPropagation = function() {
		this._stop = true
	}
	Event.prototype.replacePayload = function(payload) {
		this._replace = payload
	}

	var callbacks = []
	var addBeforeScriptExecuteListener = function(f) {
		if (!f instanceof Function) {
			throw new Error('Event handler must be a function.')
		}
		callbacks.push(f)
	}
	var removeBeforeScriptExecuteListener = function(f) {
		var i = callbacks.length
		while (i--) {
			if (callbacks[i] === f) {
				callbacks.splice(i, 1)
			}
		}
	}
	var addev = window.addEventListener.bind(window)
	var rmev = window.removeEventListener.bind(window)
	window.addEventListener = function() {
		if (arguments[0].toLowerCase() === 'beforescriptexecute') addBeforeScriptExecuteListener(arguments[1])
		else addev.apply(null, arguments)
	}
	window.removeEventListener = function() {
		if (arguments[0].toLowerCase() === 'beforescriptexecute') removeBeforeScriptExecuteListener(arguments[1])
		else rmev.apply(null, arguments)
	}

	var dispatch = function(script, target) {
		var e = new Event(script, target)

		if (window.onbeforescriptexecute instanceof Function) {
			try {
				window.onbeforescriptexecute(e)
			} catch (err) {
				console.error(err)
			}
		}

		for (var i = 0; i < callbacks.length; i++) {
			if (e._stop) {
				break
			}
			try {
				callbacks[i](e)
			} catch (err) {
				console.error(err)
			}
		}

		return e
	}
	var observer = new MutationObserver(mutations => {
		for (var i = 0; i < mutations.length; i++) {
			for (var j = 0; j < mutations[i].addedNodes.length; j++) {
				var el = mutations[i].addedNodes[j]
				if (el.tagName !== 'SCRIPT') continue
				var e = dispatch(el, mutations[i].target)
				if (e._cancel) {
					el.remove()
				} else if (typeof e._replace === 'string') {
					el.textContent = e._replace
				}
			}
		}
	})
	observer.observe(document, {
		childList: true,
		subtree: true
	})
})()

## onbeforescriptexecute.min.js
!function(){function e(e,t){this.script=e,this.target=t,this._cancel=!1,this._replace=null,this._stop=!1}e.prototype.preventDefault=function(){this._cancel=!0},e.prototype.stopPropagation=function(){this._stop=!0},e.prototype.replacePayload=function(e){this._replace=e};var t=[],n=window.addEventListener.bind(window),o=window.removeEventListener.bind(window);window.addEventListener=function(){"beforescriptexecute"===arguments[0].toLowerCase()?function(e){if(!e instanceof Function)throw new Error("Event handler must be a function.");t.push(e)}(arguments[1]):n.apply(null,arguments)},window.removeEventListener=function(){"beforescriptexecute"===arguments[0].toLowerCase()?function(e){for(var n=t.length;n--;)t[n]===e&&t.splice(n,1)}(arguments[1]):o.apply(null,arguments)};var r=function(n,o){var r=new e(n,o);if(window.onbeforescriptexecute instanceof Function)try{window.onbeforescriptexecute(r)}catch(e){console.error(e)}for(var i=0;i<t.length&&!r._stop;i++)try{t[i](r)}catch(e){console.error(e)}return r};new MutationObserver(e=>{for(var t=0;t<e.length;t++)for(var n=0;n<e[t].addedNodes.length;n++){var o=e[t].addedNodes[n];if("SCRIPT"===o.tagName){var i=r(o,e[t].target);i._cancel?o.remove():"string"==typeof i._replace&&(o.textContent=i._replace)}}}).observe(document,{childList:!0,subtree:!0})}();

## test.html
<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<meta http-equiv="X-UA-Compatible" content="ie=edge">
	<title>Document</title>
</head>
<body>
	<script src="onbeforescriptexecute.js"></script>
	<script>
	window.addEventListener('beforescriptexecute',e => {
		if (e.script.textContent.includes('alert')) {
			e.preventDefault()
		}
		else if (e.script.innerHTML.includes('hello')) {
			e.replacePayload(e.script.innerHTML.replace(/hello/g, 'world'))
		}
		else if (e.script.src.includes('xxx')) {
			e.preventDefault()
		}
	})
	</script>
	<script>
		// won't execute
		alert('hello')
	</script>
	<script>
		// will execute, but 'hello' will be convert to 'world'
		console.log('hello')
	</script>
	<!-- won't execute -->
	<script src="xxx.js"></script>
</body>
</html>

## xxx.js
alert('C8763')
	// 'beforescriptexecute' event [es5]
	// original version: https://gist.github.com/jspenguin2017/cd568a50128c71e515738413cd09a890

	;(function() {
	;('use strict')
	function Event(script, target) {
	this.script = script
	this.target = target

	this._cancel = false
	this._replace = null
	this._stop = false
	}
	Event.prototype.preventDefault = function() {
	this._cancel = true
	}
	Event.prototype.stopPropagation = function() {
	this._stop = true
	}
	Event.prototype.replacePayload = function(payload) {
	this._replace = payload
	}

	var callbacks = []
	var addBeforeScriptExecuteListener = function(f) {
	if (!f instanceof Function) {
	throw new Error('Event handler must be a function.')
	}
	callbacks.push(f)
	}
	var removeBeforeScriptExecuteListener = function(f) {
	var i = callbacks.length
	while (i--) {
	if (callbacks[i] === f) {
	callbacks.splice(i, 1)
	}
	}
	}
	var addev = window.addEventListener.bind(window)
	var rmev = window.removeEventListener.bind(window)
	window.addEventListener = function() {
	if (arguments[0].toLowerCase() === 'beforescriptexecute') addBeforeScriptExecuteListener(arguments[1])
	else addev.apply(null, arguments)
	}
	window.removeEventListener = function() {
	if (arguments[0].toLowerCase() === 'beforescriptexecute') removeBeforeScriptExecuteListener(arguments[1])
	else rmev.apply(null, arguments)
	}

	var dispatch = function(script, target) {
	var e = new Event(script, target)

	if (window.onbeforescriptexecute instanceof Function) {
	try {
	window.onbeforescriptexecute(e)
	} catch (err) {
	console.error(err)
	}
	}

	for (var i = 0; i < callbacks.length; i++) {
	if (e._stop) {
	break
	}
	try {
	callbacks[i](e)
	} catch (err) {
	console.error(err)
	}
	}

	return e
	}
	var observer = new MutationObserver(mutations => {
	for (var i = 0; i < mutations.length; i++) {
	for (var j = 0; j < mutations[i].addedNodes.length; j++) {
	var el = mutations[i].addedNodes[j]
	if (el.tagName !== 'SCRIPT') continue
	var e = dispatch(el, mutations[i].target)
	if (e._cancel) {
	el.remove()
	} else if (typeof e._replace === 'string') {
	el.textContent = e._replace
	}
	}
	}
	})
	observer.observe(document, {
	childList: true,
	subtree: true
	})
	})()
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<meta http-equiv="X-UA-Compatible" content="ie=edge">
	<title>Document</title>
	</head>
	<body>
	<script src="onbeforescriptexecute.js"></script>
	<script>
	window.addEventListener('beforescriptexecute',e => {
	if (e.script.textContent.includes('alert')) {
	e.preventDefault()
	}
	else if (e.script.innerHTML.includes('hello')) {
	e.replacePayload(e.script.innerHTML.replace(/hello/g, 'world'))
	}
	else if (e.script.src.includes('xxx')) {
	e.preventDefault()
	}
	})
	</script>
	<script>
	// won't execute
	alert('hello')
	</script>
	<script>
	// will execute, but 'hello' will be convert to 'world'
	console.log('hello')
	</script>
	<!-- won't execute -->
	<script src="xxx.js"></script>
	</body>
	</html>