VueJS = Uncaught TypeError: Cannot read property 'settings' of undefined

Question

I have a basic input that should update a data on input change, but it doesn't because it returns Uncaught TypeError: Cannot read property 'settings' of undefined

Vue component

<template>
    <div>
        <div class="inner_container">
          <p>
            URL:
            <span>{{settings.url}}</span>
          </p>
          <div class="input_row">
            <input
              class="input_text"
              id="getURL"
              type="url"
              inputmode="url"
              placeholder="Enter URL"
              title="URL"
              @input="changeUrl"
            />
            <label class="label_" for="getURL">URL Link</label>
          </div>
          <button class="button" @click="saveSettings">Save all Values</button>
        </div>
    <div>
</template>

<script>
import axios from "axios";
import _ from "lodash";

export default {
  name: "Home",
  data() {
    return {
      settings: {
        brightness: "",
      },
    };
  },
  methods: {
    changeUrl: _.debounce((e) => {
      this.settings.url = e.target.value;
    }, 500),
  },
};
</script>

On each input change I receive the above error.

What am I doing wrong?

Answer 1

The problem is that this in the arrow function is not referring to the object you want. One solution is to use a normal function and predefine the property url in settings :

 new Vue({ el: '#app', data() { return { settings: { brightness: "", url: "" }, }; }, methods: { changeUrl: _.debounce(function(e) { this.settings.url = e.target.value; }, 500), saveSettings(){ } }, })

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.19/lodash.min.js"></script> <script src="https://unpkg.com/vue/dist/vue.min.js"></script> <div id="app"> <div class="inner_container"> <p> URL: <span>{{settings.url}}</span> </p> <div class="input_row"> <input class="input_text" id="getURL" type="url" inputmode="url" placeholder="Enter URL" title="URL" @input="changeUrl" /> <label class="label_" for="getURL">URL Link</label> </div> <button class="button" @click="saveSettings">Save all Values</button> </div> </div>

A simpler approach you may find useful is to set the variable using v-model :

 new Vue({ el: '#app', data() { return { settings: { brightness: "", }, }; }, methods: { saveSettings(){ } }, })

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.19/lodash.min.js"></script> <script src="https://unpkg.com/vue/dist/vue.min.js"></script> <div id="app"> <div class="inner_container"> <p> URL: <span>{{settings.url}}</span> </p> <div class="input_row"> <input class="input_text" id="getURL" type="url" inputmode="url" placeholder="Enter URL" title="URL" v-model="settings.url" /> <label class="label_" for="getURL">URL Link</label> </div> <button class="button" @click="saveSettings">Save all Values</button> </div> </div>

Answer 2

Ciao, try to use debounce like this:

_.debounce(function(e) {
  this.settings.url = e.target.value;
}, 500)

Answer 3

The problem is that you are using this in a statement that is not being called on a JS class. Fix this by changing the this to a variable name, and setting that variable name to a class.