Run results for: getElementById vs HTML5 global variable based on id value

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 16_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.0 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 16

Operating system: iOS 16.0

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
getElementById each time	4.8 Ops/sec
Own global variable	4.8 Ops/sec
Own global variable with equal name	4.8 Ops/sec
HTML5 global variable based on id value	4.7 Ops/sec

HTML Preparation code:

<table id="testTable">
</table>

Script Preparation code:

// some elemens without id
for(var i=0; i<5000; ++i)
  testTable.insertRow(-1).insertCell(-1).textContent = 'Row #'+i;

// some elements with id
var parent = testTable.parentElement;
for(var i=0; i<5000; ++i)
{
  var div = document.createElement('div');
  div.id = 'divBefore'+i;
  parent.insertBefore(div, testTable);
  
  div = document.createElement('div');
  div.id = 'divAfter'+i;
  parent.appendChild(div);
}

Tests:

getElementById each time
for(var i=0; i<10000; ++i) { var table = document.getElementById('testTable'); table.rows[0].cells[0].textContent = 'Test'; }
Own global variable
var table = document.getElementById('testTable'); for(var i=0; i<10000; ++i) { table.rows[0].cells[0].textContent = 'Test'; }
Own global variable with equal name
var testTable = document.getElementById('testTable'); for(var i=0; i<10000; ++i) { testTable.rows[0].cells[0].textContent = 'Test'; }
HTML5 global variable based on id value
for(var i=0; i<10000; ++i) { testTable.rows[0].cells[0].textContent = 'Test'; }

Run results for: getElementById vs HTML5 global variable based on id value

https://html.spec.whatwg.org/#named-access-on-the-window-object

getElementById each time

Own global variable

Own global variable with equal name

HTML5 global variable based on id value