[Vuejs]-Fetch based on if stetement

let url = ''
let pageUrl = 'https://api.chucknorris.io/jokes/random'

if(selectedCat) {
  url = `{pageUrl}?category=${this.selectedCat}`
} else {
  url = pageUrl
}

fetchJoke(url)

To make it work you need also to add url parameter to fetchJoke func which will be passed to fetch func

Instead of adding fetch in if condition, create the URL dynamically.

fetchJoke: function() {
  let url = `https://api.chucknorris.io/jokes/random`;

  if(this.selectedCat) {
    url = url + `?category=${this.selectedCat}`;
  } 

  fetch(url)
    .then(response => {
      return response.json();
    })
    .then(jsonOBj => {
      this.joke = jsonOBj.value;
    })
    .catch(error => {
      console.log(error);
    });
}

OR

fetchJoke: function() {
  fetch(`https://api.chucknorris.io/jokes/random${this.selectedCat ? '?category=' +this.selectedCat: ''}`)
    .then(response => {
      return response.json();
    })
    .then(jsonOBj => {
      this.joke = jsonOBj.value;
    })
    .catch(error => {
      console.log(error);
    });
}