js获取url参数

function getParam(key) {
    var tmp = location.search; 
    tmp = decodeURIComponent(tmp);
    var index = tmp.indexOf(key); 
    var length = key.length;     
    var value;
    if(index != -1){
        var start = index+length+1; 
        var end = tmp.indexOf(‘&‘,start);
        if(end == -1){
           value = tmp.slice(start);
        }
        else{
            value = tmp.slice(start,end);
        }        
    }
    else{
        value = ‘‘;
    }    
    return value;
}

console.log( getParam(‘userid‘) ); // xxx