:class="{ 'active': isActive }"

:class="{'active':isActive==-1}"

:class="{'active':isActive==index}"

:class="{ 'active': isActive, 'sort': isSort }"

//也可以把后面绑定的对象写在一个变量放在data里面，可以变成下面这样
:class="classObject"
data() {
 return {
  classObject:{ active: true, sort:false }
 }
}

:class="classObject"
data() {
 return {
  isActive: true,
  isSort: false
 }
},
computed: {
 classObject: function () {
  return {
   active: this.isActive,
   sort:this.isSort
  }
 }
}

:class="[isActive,isSort]"
data() {
 return{
  isActive:'active',
  isSort:'sort'
 }
}

:class="[isActive"

:class="[isActive==1"

:class="[isActive==index"

:class="[isActive==index"

//前面这个active在对象里面可以不加单引号，后面这个sort要加单引号
:class="[{ active: isActive }, 'sort']"

:class="[{ active: isActive==1 }, 'sort']"

:class="[{ active: isActive==index }, 'sort']"