我的角码出了什么问题？我得到以下错误：
无法读取BrowserDomAdapter.RemoveClass中未定义的属性“Remove”
<ol>
<li *ngClass="{active: step==='step1'}" (click)="step='step1'">Step1</li>
<li *ngClass="{active: step==='step2'}" (click)="step='step2'">Step2</li>
<li *ngClass="{active: step==='step3'}" (click)="step='step3'">Step3</li>
</ol>
Angular版本2+提供了几种有条件添加类的方式：
类型一
[class.my-class]="step === 'step1'"
类型二
[ngClass]="{'my-class': step === 'step1'}"
和多个选项：
[ngClass]="{'my-class': step === 'step1', 'my-class2':step === 'step2' }"
类型三
[ngClass]="{1:'my-class1',2:'my-class2',3:'my-class4'}[step]"
类型四
[ngClass]="(step=='step1')?'my-class1':'my-class2'"
[ngClass]=...而不是*ngClass。
*仅用于结构指令的速记语法，例如，您可以在其中使用
<div *ngFor="let item of items">{{item}}</div>
而不是较长的等效版本
<template ngFor let-item [ngForOf]="items">
<div>{{item}}</div>
</template>
另请参见https://angular.io/docs/ts/latest/api/common/index/ngclass-directive.html
<some-element [ngClass]="'first second'">...</some-element>
<some-element [ngClass]="['first', 'second']">...</some-element>
<some-element [ngClass]="{'first': true, 'second': true, 'third': false}">...</some-element>
<some-element [ngClass]="stringExp|arrayExp|objExp">...</some-element>
<some-element [ngClass]="{'class1 class2 class3' : true}">...</some-element>
另请参见https://angular.io/docs/ts/latest/guide/template-syntax.html
<!-- toggle the "special" class on/off with a property -->
<div [class.special]="isSpecial">The class binding is special</div>
<!-- binding to `class.special` trumps the class attribute -->
<div class="special"
[class.special]="!isSpecial">This one is not so special</div>
<!-- reset/override all class names with a binding -->
<div class="bad curly special"
[class]="badCurly">Bad curly</div>
