Guard Clause

guard-clause.js

// Guard Clause is a technique derived from the fail-fast method 
// whose purpose is to validate a condition and immediately stop the code execution 
// about the result of the validation.
// Using guard clauses is a common and clean technique for simplifying the code block and avoiding unnecessary complexity.

// Example 1
const submitForm = (formData, formMeta) => {
  if (!formMeta.hasError(formData)) {
    formData.submit(); 
  }
}

const submitFormWithGuardClause = (formData, formMeta) => {
  if (formMeta.hasError(formData)) {
    return;
  }
  
  formData.submit();
}

// Example 2
if (hasSubscription) {
    if (email === contact.email) {
        const isUpdated = this.db
            .where('email', $email)
            .where('is_subscribed', !isSubscribed)
            .update({
                'is_subscribed': isSubscribed,
            });

        if (isUpdated) {
            if (hasSubscription) {
                event(new Subscribed(email));
            } else {
                event(new Unsubscribed(email));
            }
        }
    }
}

// with guard clause 
if (!hasSubscription) {
  return; 
}

if (email !== contact.email) {
  return;
}

const isUpdated = this.db
  .where('email', $email)
  .where('is_subscribed', !isSubscribed)
  .update({
      'is_subscribed': isSubscribed,
  });

if (!isUpdated) {
  return; 
}

const instance = hasSubscription ? new Subscribed(email) : new Unsubscribed(email);
event(instance);