Selectors API 544
The querySelector() Method 544
The querySelectorAll() Method 544
The matches() Method 545
Element Traversal 546
HTML5 547
Class-Related Additions 547
 The getElementsByClassName() Method 547
 The classList Property 548
Focus Management 549
Changes to HTMLDocument 550
 The readyState Property 550
 Compatibility Mode 550
 The head Property 551
Character Set Properties 551
Custom Data Attributes 551
Markup Insertion 552
 The innerHTML Property 552
 Using innerHTML in Legacy Internet Explorer 553
 The outerHTML Property 554
 The insertAdjacentHTML() and insertAdjacentText() Methods 555
 Memory and Performance Issues 555
 Cross-Site Scripting Considerations 556
The scrollIntoView() Method 556
Proprietary Extensions 557
The children Property 557
The contains() Method 557
Markup Insertion 558
 The innerText Property 558
 The outerText Property 560
Scrolling 560
Summary 560

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document.activeElement，document.hasFocus()，document.characterSet，scrollIntoView()