# 1 ： *ngFor --- 数据循环
No 1：*ngFor普通循环
No 2：循环时设置序列号
No 3：template循环数据
<ul>
<li *ngFor ="let item of list; let key = index">
{{key} -- {{item}}
</li>
</ul>
<ul>
<li template =" ngFor let item of list2; let key = index">
{{key} -- {{item.name}}
</li>
</ul>
# 2 : *ngIf --- 条件判断
<div *ngIf = "flag">
flag=true的情况下显示
</div>
<p template="ngIf list.length > 3">数组长度大于三时显示</p>
# 3: *ngSwitchCase --- 多重选择
<div [ngSwitch] = "answer">
<p *ngSwitchCase = " 'a' "> A </p>
<p * ngSwitchCase = " 'b' ">B </p>
<p *ngSwitchDefault> 请输入正确答案</p>
</div>
