How to find the corresponding Id for parameter passed into a new page for saving via Sharepoint api

Question

Overnight, with the help of this forum, I figured out how to save a parameter passed via a query string to my Sharepoint api call for "Name" field. I'd like to take this one step further, and instead of saving "Name", I want to save the "Id" that corresponds to the "Name". I know that "Name" is a Lookup field in my list.

The line of code I'm struggling with is this:

var siteIdFromParameter =   getSiteParam('Site', _spPageContextInfo.webAbsoluteUrl)?$Id="/_api/web/lists(guid'<guid>')"

Here's all my code:

        function getSiteVars() {
             var vars = {};
                var parts = window.location.href.replace(/[?&]+([^=&]+)=([^&]*)/gi, function(m,key,value) {
                vars[key] = value;
                });
            return vars;
        }

        function getSiteParam(parameter, defaultvalue){
            var siteparameter = defaultvalue;
            if(window.location.href.indexOf(parameter) > -1){
            siteparameter = getSiteVars()[parameter];
        }
            return getSiteParam;
    }


    function addFeatureSuggestion() {

        var siteNameFromParameter = getSiteParam('Site', _spPageContextInfo.webAbsoluteUrl);
        var siteIdFromParameter =   getSiteParam('Site', _spPageContextInfo.webAbsoluteUrl)?$Id="/_api/web/lists(guid'<guid>')"

        var item = {
            "__metadata": { "type": "SP.Data.AddListItem" },
            "SiteId": siteIdFromParameter,
            "Title": $('#inputTitle').val()
        };

Answer 1

To get the Id of the Site, you will need to make a separate web service call to /_api/Web before you save your new Item. If you are using .ajax to make your service calls, make sure to do your next step inside the .then or .done method since it is an asynchronous call. Note, this presumes that SiteUrl is a valid SharePoint site that the current user has at least read access to.

function getSiteVars() {
     var vars = {};
        var parts = window.location.href.replace(/[?&]+([^=&]+)=([^&]*)/gi, function(m,key,value) {
        vars[key] = value;
        });
    return vars;
}

function getSiteParam(parameter, defaultvalue){
    var siteparameter = defaultvalue;
    if(window.location.href.indexOf(parameter) > -1){
    siteparameter = getSiteVars()[parameter];
}
    return getSiteParam;
}


function addFeatureSuggestion() {
    var siteUrlFromParameter = getSiteParam('Site', _spPageContextInfo.webAbsoluteUrl);

    $.ajax({
        url: siteUrlFromParameter + "/_api/Web",
        type: "GET",
        contentType: "application/json;odata=verbose",
        headers: {
            "Accept": "application/json;odata=verbose",
            "X-RequestDigest": $("#__REQUESTDIGEST").val()
        },
    }).then(function (data) {
        var siteIdFromParameter = data.d.results[0].Id;

        var item = {
            "__metadata": { "type": "SP.Data.AddListItem" },
            "SiteId": siteIdFromParameter,
            "Title": $('#inputTitle').val()
        };

        // do the rest of your item saving in here
    });
}