vue2.x版详解computed和watch的使用

<li>computed基本使用</li>
<li>name值：{{ name }}</li>
<li>{{ changeName }}</li>
data() {
		return {
			name: "zhangsan",
		};
	},
computed: {
	changeName: function () {
		return `一段依赖于name：${this.name}的文字`;
	},
},

<li>{{ isCache }}</li>
<li>{{ cacheTip }}</li>
<li>{{ changeCache }}</li>
<li><button @click="handleChange">修改文字</button></li>
data() {
	return {
		cacheTip: "cacheTip原始值",
	};
},
computed: {
	isCache: function () {
		return `不依赖于任何属性值的一段文字`;
	},
	changeCache: function () {
		return `依赖于cacheTip，${this.cacheTip}`;
	},
},
methods: {
	handleChange() {
		this.cacheTip = "cacheTip状态被修改";
	},
},

isCache: {
    setter:function () {
    	return `不依赖于任何属性值的一段文字`;
    }
}

<li>{{ firstName }}</li>
<li>{{ lastName }}</li>
<li>{{ setterGetter }}</li>
<li><button @click="handleChangeFirst">修改文字</button></li>
data() {
	return {
		firstName: "lewyon001",
		lastName: "布欧001",
	};
},
computed: {
    setterGetter: {
    	// getter
    	get: function (newValue) {
    		console.log("newValue", newValue);
    		return this.firstName + " " + this.lastName;
    	},
    	// setter
    	set: function (newValue) {
    		console.log("newValue", newValue);
    		this.firstName = `${newValue.firstName}`;
    		this.lastName = `${newValue.lastName}`;
    	},
    },
}

methods: {
	handleChangeFirst() {
		this.setterGetter = { firstName: "lewyon", lastName: "布欧" };
	},
},

<li>name值：{{ name }}</li>
<li>{{ nameTip }}</li>
<li>通过异步操作获取的age：{{ age }}</li>
<li><button @click="getUser">修改名字</button></li>
let p1 = new Promise((resolve, reject) => {
	resolve({ age: "14" });
});
data() {
	return {
		name: "zhangsan",
		nameTip: "name未改变",
	};
},
watch: {
	name(newVal, oldVal) {
		// watch可以监听一些状态发生更改的时候，做一些处理，修改状态，或者异步操作
		this.nameTip = "name状态改变了";
		this.getData();
	},
},
methods: {
	getData() {
		setTimeout(() => {
			this.getAge();
		}, 1000);
	},
	getUser() {
		this.name = "lisi";
	},
	getAge() {
		p1.then((res) => {
			console.log(res);
			this.age = res.age;
		});
	},
},

<li>{{ immediateNameTip }}</li>
 
data() {
	return {
		immediateName: "immediateName原始值",
		immediateNameTip: "immediateName改变时的提示文字",
	};
},
 
immediateName: {
    handler(newVal, oldVal) {
    	console.log("immediate表示最初监听值得时候，也执行这段代码");
    	setTimeout(() => {
    		this.immediateNameTip =
    			"immediateName添加immediate，初次绑定也会执行";
    	}, 2000);
    },
    immediate: true,
    deep: true, // 只针对对象的深层次属性变化
},