What is the difference between ng-class and ng-style?
From the official Docs: https://angular.io/api/common/NgClass
These are different ways to use ngClass
...
<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>
2. Similarly with ngStyle you can do the following:
**< some-element [ngStyle]="{'font-style': styleExp}">...</some-element>**
Your styleExp can be anything that evaluates to a legal value for the attribute you are setting ,e.g. font-size in the example above
Alternatively,
****< some-element [ngStyle]="objExp">...****
Where objExp is an object containing key-value pairs of your style attributes e.g. { width: 40, margin: '2em' } etc.
ng-style is used to interpolate javascript object into style attribute, not css class.
Following directive will be translated to style="color:red"
ng-style="{color: 'red'}"
And ng-class directive translates your object into class attribute.
Following will be translated to class="deleted" when isDeleted variable is true.
ng-class="{'deleted': isDeleted}"
Note:
There is one more use case for ng-style. If you want to interpolate something in style attribute, you should consider using ng-style. Otherwise, that would not work before Internet Explorer 11 as documentation suggests.
So, instead of using style:
style="width: {{progress}}"
Use ng-style:
ng-style="{'width':progress}"
In ng-class you are loading a CSS class defined in some place, like Bootstrap. In ng-style you are setting the CSS style that you want that element has, example:
ng-style="{ 'background-color': person.email == selectedPerson.email ? 'lightgray' : ' '}" //background-color is a style
has-error is a class defined in somewhere that is composed by style(s):
ng-class="{ 'has-error’: !theForm.email.$valid, 'has-success':theForm.email.$valid}