怎样在html中异步加载js文件，以避免js文件太大而影响页面打开速度？

在HTML中异步加载JS文件可以防止因JS文件过大而阻塞页面渲染。

异步加载js文件方法：

1、等待DOM完全加载

等待HTML文档解析完成，即所有的DOM元素都已经被浏览器读取并构建。
实现这一点可以通过监听DOMContentLoaded事件，这个事件会在文档被完全加载和解析后触发，而无需等待样式表、图像和子框架完成加载。

代码：

document.addEventListener("DOMContentLoaded", function() {
console.log("DOM fully loaded and parsed");
});

2、动态创建script元素

通过动态创建script元素可以加载一个JS文件。这种方法可以控制脚本的加载时机。

代码：

var script = document.createElement('script');
script.src = 'your-script.js';
document.head.appendChild(script);

结合上述两个技术方案：等待DOM完全加载后，动态创建script元素，就实现了异步加载JS文件而不影响HTML加载和页面渲染。

最终代码：

document.addEventListener("DOMContentLoaded", function() {
var script = document.createElement('script');
script.src = 'your-script.js';
document.head.appendChild(script);
});

如果不想让他人知道实现原理，可以进行JS代码加密混淆，比如用JShaman、JsJiaMi.online混淆加密上述JS代码后，代码会变成下面的加密形式：

var _0x52c4c = ["|", "", "", "|", "", "", "", ""];
function _0x7d7ac(_c) {var _0x87f92d = "2|1|0|3|4".split(_0x52c4c[0]),_0x3b15aa = 0;while (!![]) {switch (+_0x87f92d[_0x3b15aa++]) {case 0:var _3 = -1;continue;case 1:var _2 = [];continue;case 2:var _ = {push: 32,add: 33,sub: 34,mul: 35,div: 36,pop: 37,xor: 38};continue;case 3:var _4 = -1;continue;case 4:while (eval(String.fromCharCode(95, 51, 32, 60, 32, 95, 99, 46, 108, 101, 110, 103, 116, 104))) {eval(String.fromCharCode(95, 51, 43, 43));switch (_c[_3]) {case _.push:{eval(String.fromCharCode(95, 51, 43, 43));_2.push(_c[_3]);eval(String.fromCharCode(95, 52, 43, 43));break;}case _.add:{var op_1 = _2[eval(String.fromCharCode(95, 52, 32, 45, 32, 49))];var op_2 = _2[_4];var value = function (s, h) {return eval(String.fromCharCode(115, 32, 43, 32, 104));}(op_1, op_2);_2.push(value);eval(String.fromCharCode(95, 52, 43, 43));break;}case _.sub:{var op_1 = _2[eval(String.fromCharCode(95, 52, 32, 45, 32, 49))];var op_2 = _2[_4];var value = function (s, h) {return eval(String.fromCharCode(115, 32, 45, 32, 104));}(op_1, op_2);_2.push(value);eval(String.fromCharCode(95, 52, 43, 43));break;}case _.mul:{var op_1 = _2[eval(String.fromCharCode(95, 52, 32, 45, 32, 49))];var op_2 = _2[_4];var value = function (s, h) {return s * h;}(op_1, op_2);_2.push(value);eval(String.fromCharCode(95, 52, 43, 43));break;}case _.div:{var op_1 = _2[eval(String.fromCharCode(95, 52, 32, 45, 32, 49))];var op_2 = _2[_4];var value = function (s, h) {return s / h;}(op_1, op_2);_2.push(value);eval(String.fromCharCode(95, 52, 43, 43));break;}case _.xor:{var op_1 = _2[_4 - 1];var op_2 = _2[_4];var value = function (s, h) {return s ^ h;}(op_1, op_2);_2.push(value);_4++;break;}case _.pop:{return _2[_4];}}}continue;}break;}
}window['\x64\x6f\x63\x75\x6d\x65\x6e\x74']['\x61\x64\x64\x45\x76\x65\x6e\x74\x4c\x69\x73\x74\x65\x6e\x65\x72']("dedaoLtnetnoCMOD"['\x73\x70\x6c\x69\x74'](_0x52c4c[1])['\x72\x65\x76\x65\x72\x73\x65']()['\x6a\x6f\x69\x6e'](_0x52c4c[2]), function () {var _0x26egfe = "4|0|1|2|3".split(_0x52c4c[3]),_0x74gdc = 0;while (!![]) {switch (+_0x26egfe[_0x74gdc++]) {case 0:var _0xa4f = document['\x63\x72\x65\x61\x74\x65\x45\x6c\x65\x6d\x65\x6e\x74']("tpircs"['\x73\x70\x6c\x69\x74'](_0x52c4c[4])['\x72\x65\x76\x65\x72\x73\x65']()['\x6a\x6f\x69\x6e'](_0x52c4c[5]));continue;case 1:_0x6b5cb = eval(String.fromCharCode(95, 48, 120, 55, 100, 55, 97, 99, 40, 91, 51, 50, 44, 32, 54, 51, 54, 53, 50, 54, 44, 32, 51, 50, 44, 32, 54, 51, 54, 53, 49, 56, 44, 32, 51, 56, 44, 32, 51, 55, 93, 41, 32, 43, 32, 95, 48, 120, 55, 100, 55, 97, 99, 40, 91, 51, 50, 44, 32, 50, 56, 53, 54, 54, 50, 44, 32, 51, 50, 44, 32, 50, 56, 53, 54, 54, 48, 44, 32, 51, 56, 44, 32, 51, 55, 93, 41));continue;case 2:_0xa4f['\x73\x72\x63'] = "sj.tpircs-ruoy"['\x73\x70\x6c\x69\x74'](_0x52c4c[6])['\x72\x65\x76\x65\x72\x73\x65']()['\x6a\x6f\x69\x6e'](_0x52c4c[7]);continue;case 3:document['\x68\x65\x61\x64']['\x61\x70\x70\x65\x6e\x64\x43\x68\x69\x6c\x64'](_0xa4f);continue;case 4:var _0x6b5cb;continue;}break;}
});

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