add loadScript to Analytics

packages/browser/src/core/analytics/index.ts

@@ -252,6 +252,63 @@ export class Analytics
     return this._universalStorage
   }
 
+  loadScript(
+    src: string,
+    attributes?: Record<string, string>
+  ): Promise<HTMLScriptElement> {
+    function findScript(src: string): HTMLScriptElement | undefined {
+      const scripts = Array.prototype.slice.call(
+        window.document.querySelectorAll('script')
+      )
+      return scripts.find((s) => s.src === src)
+    }
+
+    const found = findScript(src)
+
+    if (found !== undefined) {
+      const status = found?.getAttribute('status')
+
+      if (status === 'loaded') {
+        return Promise.resolve(found)
+      }
+
+      if (status === 'loading') {
+        return new Promise((resolve, reject) => {
+          found.addEventListener('load', () => resolve(found))
+          found.addEventListener('error', (err) => reject(err))
+        })
+      }
+    }
+
+    return new Promise((resolve, reject) => {
+      const script = window.document.createElement('script')
+
+      script.type = 'text/javascript'
+      script.src = src
+      script.async = true
+
+      script.setAttribute('status', 'loading')
+      for (const [k, v] of Object.entries(attributes ?? {})) {
+        script.setAttribute(k, v)
+      }
+
+      script.onload = (): void => {
+        script.onerror = script.onload = null
+        script.setAttribute('status', 'loaded')
+        resolve(script)
+      }
+
+      script.onerror = (): void => {
+        script.onerror = script.onload = null
+        script.setAttribute('status', 'error')
+        reject(new Error(`Failed to load ${src}`))
+      }
+
+      const tag = window.document.getElementsByTagName('script')[0]
+      tag.parentElement?.insertBefore(script, tag)
+    })
+  }
+
   async track(...args: EventParams): Promise<DispatchedEvent> {
     const [name, data, opts, cb] = resolveArguments(...args)