特定のURLへの遷移リンクにGETパラメータを引き継ぐJS

keep-get-queries

window.onload = function setCvQuearyOnLoad() {
    var param = GetQueryString();
    var target_param = "key";
    var target_val = "";
    var target_url = "example.com";

    if (param != null && param[target_param] != undefined) {
        target_val = param[target_param];
        var ankers = document.getElementsByTagName('a');
        for (i = 0; i < ankers.length; i++) {
            var href = ankers[i].href;
            if (href.indexOf(target_url) === 0) {
                var glue = href.indexOf('?') === -1 ? '?' : '&';
                ankers[i].href = href + glue + target_param + '=' + target_val;
            }
        }

    }
}

function GetQueryString() {
    if (1 < document.location.search.length) {
        var query = document.location.search.substring(1);
        var parameters = query.split('&');

        var result = new Object();
        for (var i = 0; i < parameters.length; i++) {
            var element = parameters[i].split('=');

            var paramName = decodeURIComponent(element[0]);
            var paramValue = decodeURIComponent(element[1]);

            result[paramName] = decodeURIComponent(paramValue);
        }
        return result;
    }
    return null;
}