Erros when adding to SP list through AngularJS.

I'm just trying to submit a simple item to a sharepoint online list. Here's the code I have to do this.

app.factory("organizationsSrvc", ['$rootScope', '$http',
function($rootScope, $http) {
var listName = "Organizations";
var organizationsService = {};
//Organization operations
var organizations = null;
organizationsService.add = function(organization) {
var data = JSON.stringify(organization);
data = data.replace(/[{}]/g, '');
var datavalue = "{__metadata:{'type':'SP.Data.'" + listName + "'.ListItem'}," + data + "}";
console.log(datavalue);
$http({
url: _spPageContextInfo.webAbsoluteUrl + "/_api/web/lists/GetByTitle('" + listName + "')/items",
method: 'POST',
headers: {
"Accept": "application/json;odata=verbose",
"Content-Type": "application/json;odata=verbose",
"X-RequestDigest": $("#__REQUESTDIGEST").val(),
"X-HTTP-Method": "POST"
},
data: datavalue
}).then(function success(response) {
console.log("[add Organization] POST worked");
console.log("[add Organization] New Id = " + response.Id);
debugger;
}, function error(response) {
console.log("[add Organization] Error = " + response);
debugger;
})
console.log($http);
debugger;
};
return organizationsService;
}]);

When running this I get the following output in console.

{__metadata:{'type':'SP.Data.'Organizations'.ListItem'},"title":"test"}

organizations.controller.js:69 ƒ $http(requestConfig) {

if (!angular.isObject(requestConfig)) {

throw minErr('$http')('badreq', 'Http request configuration must be an object. Received: {0}', requestConfig);

…

POST ....... 400

From what I'm seeing in this output, it looks like It's outputting line 14, then line 33, then hits the error on line 31. It's saying it's a 400 error.

Any help is appreciated!!