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Vue / Browser — Alias

Link an alias (e.g. anonymous ID) to the current user. Use this to merge anonymous events (from before login) with the identified user.

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alias(alias)

Links an alias to the current user. Sends a $create_alias event.
ParameterTypeRequiredDescription
aliasstringyesAlias to link (e.g. previous anonymous ID)
When to use: After login to merge anonymous events (from before login) with the identified user. This ensures all events are associated with the same user profile.

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Vue example

<script setup>
import { onMounted, ref } from 'vue'
import { createSignal } from '@signal-js/browser'

let signal = null
const anonymousId = ref(null)

onMounted(async () => {
  signal = createSignal({ endpoint: '...', apiKey: '...', projectId: '...' })
  await signal.start()
  
  // Store anonymous ID before login
  const stored = localStorage.getItem('anonymous_id')
  if (stored) {
    anonymousId.value = stored
  }
})

function handleLogin(userId, userTraits) {
  // Identify the user
  signal?.identify(userId, userTraits)
  
  // Link anonymous ID if it exists
  if (anonymousId.value) {
    signal?.alias(anonymousId.value)
    localStorage.removeItem('anonymous_id')
  }
}
</script>

<template>
  <button @click="handleLogin('user_123', { email: 'user@example.com' })">
    Log in
  </button>
</template>

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Vanilla JS example

const signal = createSignal({ endpoint: '...', apiKey: '...', projectId: '...' });
await signal.start();

// Store anonymous ID before login
let anonymousId = localStorage.getItem('anonymous_id') || null;

function handleLogin(userId, userTraits) {
  // Identify the user
  signal.identify(userId, userTraits);
  
  // Link anonymous ID if it exists
  if (anonymousId) {
    signal.alias(anonymousId);
    localStorage.removeItem('anonymous_id');
  }
}

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How it works

  1. Before login: User browses anonymously. Events are tracked with an anonymous ID.
  2. After login: Call identify(userId, traits) to set the user’s identity.
  3. Link alias: Call alias(anonymousId) to link the anonymous ID to the identified user.
  4. Result: All events (both anonymous and identified) are now associated with the same user profile.

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See also