替换JavaScript函数

Question

有一个JavaScript文件附加到页面的源代码，我想使用TamperMonkey编辑和覆盖它的一个函数，所以我可以改变函数的功能，这可能吗？ 这是功能：

function handleNext () {
        switch(curIndex){
        case 0:
            startLoading();
            $.getJSON(API_URL + getSubdomain() + "/names", function(res) {
                if(res.A == true) {
                    moveToSection($("#section-name-links"), $("#section-user-prefrences"));
                } else {
                    finishLoading();
                    displayError("Incorrect");
                }

            }).fail(function() {
                finishLoading();
                displayError("An error occured");
            });
            break;
        case 1:
            startLoading();
            var success = true;
            if($("#prefrences input[name=name]").val() == ""){
                displayError("Please enter your name");
                success = false;
            }
            if($("#section-user-prefrences input[surname=surname]").size() > 0 && 
                $("#section-user-prefrences input[surname=surname]:checked").size() == 0){
                displayError("Please enter your last name");
                success = false;
            }
            if(!success){
                finishLoading();
                return;
            }
            var rewardid = $("#section-user-prefrences input[name=reward]:checked").val();
            $.post(API_URL + getSubdomain() + "/names", {
                nameid: namesid || -1,
                username: $("#section-user-prefrences input[name=name]").val()
            }, function(res) {
                moveToSection($("#section-user-prefrences"), $("#section-thank-you"));
                $("#continue").hide();
            }).fail(function() {
                finishLoading();
                displayError("An error occured");
            });

            break;
        }
    }

我的目标是将功能改为：

    function handleNext () {
        switch(curIndex){
        case 0:
            startLoading();

                    moveToSection($("#section-name-links"), $("#section-user-prefrences"));

            }).fail(function() {
                finishLoading();
                displayError("An error occured");
            });
            break;
        case 1:
            startLoading();
            var success = true;
            if(!success){
                finishLoading();
                return;
            }

            break;
        }
    }