Angular – How can I write a condition in interpolation?

You can use nested ternary if

{{element.source == 1 ? 'upwork' : (element.source == 2 ? 'refer from friend' : '')}}

or probably better

export class MyComponent {
  sourceNames = {1: 'upwork', 2: 'refer from friend', 3: 'other' };
}

{{sourceNames[element.source]}}