How to get address bar parameters using JavaScript_javascript skills

/**
* Get address bar parameters
*
* @example GetUrlString('id')
*
* @desc Add judgment when calling to ensure that the program will not go wrong
* var myurl = GetUrlString('id');
* if (myurl != null && myurl.toString().length > 1) {
*                    alert(GetUrlString("id"));
*           }
*
* @param String param To get the parameter name in the address bar
* @return String Value
* @type String
*
* @name GetUrlString()
*
​*/
function GetUrlString(param) {
var sValue = location.search.match(new RegExp("[?&]" m "=([^&]*)(&?)", "i"));
Return sValue ? decodeURI(sValue[1]) : decodeURI(sValue);
}

window.onload = function() {
var myurl = GetParm("id");
If (myurl != null && myurl.toString().length > 1) {
alert(GetParm("id"));
}
}