延迟加载js

<script>
        $(function () {
            // 延迟加载js文件
            setTimeout(function () {
                loadScript("./js/applySecStep.js", function () { });
            }, 30);
            
            function loadScript(src, callback) {
                var script = document.createElement("script")
                script.type = "text/javascript";
                if (script.readyState) { //IE
                    script.onreadystatechange = function () {
                        if (script.readyState == "loaded" ||
                            script.readyState == "complete") {
                            script.onreadystatechange = null;
                            callback();
                        }
                    };
                } else { //Others: Firefox, Safari, Chrome, and Opera
                    script.onload = function () {
                        callback();
                    };
                }
                script.src = src;
                document.body.appendChild(script);
            }
        })
 </script>