Test array changing

by Max Sinev

HTML

<div id="app">
  <div v-for="todo in todos" :key="todo.text">
     {{todo.text}}
  </div>
  <button @click="changeItemProperty">changeItemProperty(works)</button>
  <button @click="changeItemWithAssign">changeItemWithAssign(works)</button>
  <button @click="changeItem">changeItem(does not work!)</button>
  <button @click="changeItem2">changeItem2(works)</button>
</div>

Vue

new Vue({
  el: "#app",
  data: {
    todos: [
      { text: "Learn JavaScript" },
      { text: "Learn Vue" },
      { text: "Play around in JSFiddle" },
      { text: "Build something awesome" }
    ]
  },
  methods: {
    // work because object property is reactive
  	changeItemProperty() {
    	this.todos[3].text = "changedItemProperty";
    },
    // same reason, properties are reactive
    changeItemWithAssign() {
    	Object.assign(this.todos[3], { text: "changedItemWithAssign" });
    },
    // does not work, can not track changes in array
    // also this will brake all attempts to change TEXT property in UI
    // because objects property after this is not reactive
    changeItem() {
    	this.todos[3] = { text: "changedItem" }
    },
    // works
    changeItem2() {
    	Vue.set(this.todos, 3, { text: "changedItem2" });
    }	
  }
})