一、代码

function setQueryString(key, val) { 
    var url = window.location.href.split('?'), search=url[1]; //获取地址栏 "?"后的内容
    var query = {};
    if (search) {
        search.split('&').forEach((item) => {
            var arr = item.split('=');
            query[arr[0]] = arr[1];
        });
    }
    query[key] = val;
    var queryArr = [];
    for (var p in query) {
        queryArr.push(p + '=' + query[p]);
    }
    return url[0]+'?'+queryArr.join('&');
};