Test array changing

by Max Sinev

HTML

<div id="app">
  <div v-for="todo in todos" :key="text">
     {{todo.text}}
  </div>
  <button @click="changeItemProperty">changeItemProperty</button>
  <button @click="changeItemWithAssign">changeItemWithAssign</button>
  <button @click="changeItem">changeItem</button>
  <button @click="changeItem2">changeItem2</button>
</div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

del {
  color: rgba(0, 0, 0, 0.3);
}

Vue

new Vue({
  el: "#app",
  data: {
    todos: [
      { text: "Learn JavaScript", done: false },
      { text: "Learn Vue", done: false },
      { text: "Play around in JSFiddle", done: true },
      { text: "Build something awesome", done: true }
    ]
  },
  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", done: true });
    },
    // does not work, can not track changes in array
    changeItem() {
    	this.todos[3] = { text: "changedItem", done: true }
    },
    // works
    changeItem2() {
    	Vue.set(this.todos, 3, { text: "changedItem2", done: true });
    }	
  }
})