TypeError：无法读取undefined vue-resource.js的属性'replace'：284

Can anyone please help me with this error?

I have been using jQuery along with vue.js. Below is the method I am having issue with... It is called by a post request. new_user contains values received from the html form fields...

Values are being received nicely when I write it in console.

Problem comes when I try to use ajax method to store the data (this.$http.post()). I get the following error:

TypeError: Cannot read property 'replace' of undefined vue-resource.js:284

There were couple of links I went through.but i could take help from none... I might have made some silly mistakes because I used the above code from a perfectly running script. So if anyone can spot the mistake i would be grateful. Thanks... :)

Happy coding.

    addUser : function(new_user){
        // var instance = this;
        console.log(this)
        var new_user_input = this.new_user
        console.log(new_user_input.name)//this works fine..

         //problem comes right here
         this.$http.post("clients/" , new_user_input).then((response) => {
            alert("ok")
        },(response) => {
            alert("failed")
            this.form_errors = response.data
            // console.log("here should be the form errrors " + response.data.title)
        });
    }

If your using Laravel, make sure that you have in you template:

Good:

<script>
        window.Laravel = <?php echo json_encode([
            'csrfToken' => csrf_token(),
        ]); ?>
</script>

//OR

<script>
    window.Laravel = {!! json_encode([
        'csrfToken' => csrf_token(),
    ]) !!}
</script>

BAD:

<script>
        window.Laravel = '<?php echo json_encode([
            'csrfToken' => csrf_token(),
        ]); ?>'
</script>

//OR

<script>
    window.Laravel = {{ json_encode([
        'csrfToken' => csrf_token(),
    ]) }}
</script>