title: How to pass a prop with a default value in case the prop is empty without using the prop's "default" property
body: <p>I'm using a <a href="http://kazupon.github.io/vue-i18n/started.html#html" rel="nofollow noreferrer">third party multi-language package</a> where translation values can only be obtained/used from component's template, not from component's logic (at least I can't find how to the latter).</p>
  
  <p>I need to pass such translation value in some component as a default prop value:</p>
  
  <pre><code>:placeholder="{ propValue ? propValue : $t('value') }
  </code></pre>
  
  <p>If placeholder is explicitly specified then use that. If not, use $t('value') instead. What's the right way to write this?</p>
  
  <p>I tried this in reaction to @Michael's answer:</p>
  
  <pre><code>import i18n from "@/utilities/i18n";
  export default {
    data() {
      return {
        test: i18n.t('register.agreeTermsCaptionLink')
      };
    }
  };
  </code></pre>
  
  <p>Getting this error:</p>
  
  <blockquote>
    <p>_utilities_i18n__WEBPACK_IMPORTED_MODULE_7__.default.t is not a function</p>
  </blockquote>