Undefined is not an object, when calling function inside jQuery's $.post

Inside my attemptSearch function, I use jQuery $.post to get some JSON results. I'm getting the error

Undefined is not an object

on the call

this.getSearchResults.bind(this)

I have the same set up in another web app and I don't get this error. What am I doing wrong?

var app = {
    init: function() {
        this.cacheDom();
        this.bindEvents();
    },
    cacheDom: function() {
        this.$search = $('#search');
    },
    bindEvents: function() {
        this.$search.keyup(this.attemptSearch)
    },
    searchResults : [],
    getSearchResults : function(val){       
        var currentSearchResult = val.query.search;
        for (var i = 0; i < currentSearchResult.length; i++) {
            var result = {
                title: currentSearchResult[i].title,
            }
            console.log(this.searchResults);
            this.searchResults.push(result);
        }
    },
    attemptSearch: function(event) {
        var wiki = "https://crossorigin.me/https://en.wikipedia.org/w/api.php?action=query&list=search&format=json&srsearch=";
        if (event.keyCode == 13) {
            $.post((wiki + $('#search').val()), this.getSearchResults.bind(this))
        }
    }, 
};

app.init();