Show Hints for choice lists

global.choiceUtil.si.js

//script include global.choiceUtil
//client callable true
var choiceUtil = Class.create();
choiceUtil.prototype = Object.extendsObject(AbstractAjaxProcessor, {
    getHint: function() {
        try {
            var returnObj = {};
            var hint = new GlideRecord('sys_choice');
            hint.addQuery('name', this.getParameter('sysparm_table'));
            hint.addQuery('field', this.getParameter('sysparm_field'));
            hint.addQuery('value', this.getParameter('sysparm_val'));
            hint.addQuery('inactive', 'false');
            hint.query();
            if (hint.next()) {
                returnObj.hint = hint.getValue('hint');
            } else {
                returnObj.error = 'no choice found for ' + hint.getEncodedQuery();
            }
            return JSON.stringify(returnObj);
        } catch (error) {
            return JSON.stringify(error, '', '  ');
        }
    },
    type: 'choiceUtil'
});

incident.clientscript.js

function onChange(control, oldValue, newValue, isLoading, isTemplate) {
    if (isLoading || newValue === '') {
        return;
    }
    var field = 'category';
    var ga = new GlideAjax('global.choiceUtil');
    ga.addParam('sysparm_name', 'getHint');
    ga.addParam('sysparm_table', 'incident');
    ga.addParam('sysparm_field', field);
    ga.addParam('sysparm_val', newValue);
    ga.getXML(HintParse);

    function HintParse(response) {
        var answer = JSON.parse(response.responseXML.documentElement.getAttribute("answer"));
        //console.log(answer);
        g_form.hideFieldMsg(field, true);
        if (answer.hint) {
            g_form.showFieldMsg(field, answer.hint, 'info', true);
        }
    }

}