➕ page: add focus() (close #17)

src/api/Page.ts

@@ -137,6 +137,23 @@ class Page extends EventEmitter {
     return result.value
   }
 
+  async focus (selector: string) {
+    /* istanbul ignore next */
+    return this.evaluate((sel) => {
+      const el = document.querySelector(sel as string)
+
+      if (el === null) {
+        throw new Error('Unable to find element')
+      }
+
+      if (!(el instanceof HTMLElement)) {
+        throw new Error('Found element is not HTMLElement and not focusable')
+      }
+
+      el.focus()
+    }, selector)
+  }
+
   async goto (url: string) {
     await this._send('WebDriver:Navigate', { url })
   }

test/api/Page.ts

@@ -209,6 +209,46 @@ test('Page: `evaluate()`', testWithFirefox(async (t) => {
   }
 }))
 
+test('Page: `focus()`', testWithFirefox(async (t) => {
+  const browser = await foxr.connect()
+  const page = await browser.newPage()
+
+  await page.setContent('<div><input/><svg></svg></div>')
+
+  const activeElementBefore = await page.evaluate('document.activeElement.tagName')
+
+  await page.focus('input')
+
+  const activeElementAfter = await page.evaluate('document.activeElement.tagName')
+
+  t.true(
+    activeElementBefore !== activeElementAfter && activeElementAfter === 'INPUT',
+    'should focus element'
+  )
+
+  try {
+    await page.focus('foo')
+    t.fail()
+  } catch (err) {
+    t.equal(
+      err.message,
+      'Evaluation failed: Unable to find element',
+      'should throw if there is no such an element'
+    )
+  }
+
+  try {
+    await page.focus('svg')
+    t.fail()
+  } catch (err) {
+    t.equal(
+      err.message,
+      'Evaluation failed: Found element is not HTMLElement and not focusable',
+      'should throw if found element is not focusable'
+    )
+  }
+}))
+
 test('Page: `goto()` + `url()`', testWithFirefox(async (t) => {
   const browser = await foxr.connect()
   const page = await browser.newPage()

tsconfig.json

@@ -4,7 +4,7 @@
     "allowSyntheticDefaultImports": true,
     "noEmit": true,
     "pretty": true,
-    "lib": ["esnext"],
+    "lib": ["esnext", "dom"],
     "moduleResolution": "node",
     "typeRoots": [ "types/", "node_modules/@types/" ]
   },