Why some runtime JS errors are not displayed in the console?

Hello,
In my Laravel 5.8/vuejs 2.6 app I found situations when having some runtime JS errors in my console these errors are not displayed in the console,
but app flow is just just stopped. One of such errors is below in addForumPost method :

<script>
    import {bus} from '../../../app';
    import appMixin from '../../../appMixin';
    import {focus} from 'vue-focus';
    import Vue from 'vue';
    import {retrieveAppDictionaries, getModalCalculatedHeight, getModalCalculatedWidth} from "../../../helpers/commonFuncs";
    import CKEditor from '@ckeditor/ckeditor5-vue';  //https://ckeditor.com/docs/ckeditor5/latest/builds/guides/integration/frameworks/vuejs.html
    import ClassicEditor from '@ckeditor/ckeditor5-build-classic';
    Vue.use(CKEditor);
    export default {
        data: function () {
            return {
                ...
            }
        },
        name: 'ForumView',
        directives: {focus: focus},
        created() {
           ...
        }, //  created() {
        mounted() {
           ...
        }, // mounted() {
        mixins: [appMixin],
        methods: {
            addForumPost() {
                if (this.currentLoggedUser == null || typeof this.currentLoggedUser.id == 'undefined') {
                    this.showPopupMessage("Report abuse", 'You need to login !', 'warn');
                    return;
                }
                if ( this.trim(this.new_thread_post_body) < 5 ) {
                    this.showPopupMessage("Forum Post", 'Your message must be at least 5 chars !', 'warn');
                    return;
                }
                this.message = '';
                this.is_page_loaded = false
                axios.post(window.API_VERSION_LINK + '/forum/add_forum_post', {
                    user_id: this.currentLoggedUser.id,
                    forum_post_body: this.new_thread_post_body,
                    forum_thread_id: this.singleForumThreadRow.id,
                }).then((response) => {
                    this.is_page_loaded = true
                    let forumPost= response.data.forumPost
                    debugger
                    // THE ROW BELOW stop app flow, but no error in console
                    forumPost.created_at= momentDatetime( this.getNowDateTime(), settings_js_moment_datetime_format )
                    // forumPost.created_at= this.momentDatetime( this.getNowDateTime(), settings_js_moment_datetime_format )
                    this.threadPosts.push( forumPost )
                    this.showPopupMessage("Forum", "Your post was successfully added !", 'success');
                    ...

Code (JavaScript):

Sure comment line below and I have to use this.momentDatetime in

                    forumPost.created_at= this.momentDatetime( this.getNowDateTime(), settings_js_moment_datetime_format )

Code (JavaScript):

but why I have no console error?

$ lsb_release -d; uname -r; uname -i
Description:    Ubuntu 18.04.3 LTS
4.15.0-20-generic
x86_64
Google Chrome, Version 77.0.3865.90 (Official Build) (64-bit)

Code (markup):

And seems that is not the only case, in some cases I have to debug step by step to find the error ?
Why so ?