how to detect MathML tag support (<mfrac>,<mtable>) from javascript?

Question

I can detect MathML support with:

var e = document.createElement('div');
    e.innerHTML = '<math></math>';
    var mathMLSupported = e.firstChild && "namespaceURI" in e.firstChild && e.firstChild.namespaceURI == 'http://www.w3.org/1998/Math/MathML';

but how to detect support for <mfrac> and <mtable> ?

Answer 1

Following this document conforming browsers must implement several properties (a.k.a. bindings) for specific MathML elements in the DOM. You can therefore simply create a MathML mtable element and check, if the browser adds, e.g., the rowalign property:

var tmp = document.createElementNS('http://www.w3.org/1998/Math/MathML',
                                   'mtable');
if (tmp.hasOwnProperty('rowalign')) {
  return true;
} else {
  return false;
}

Answer 2

In jqmath, I construct a hidden <mfrac> element and compare its computed height to that of a non-fraction. See the M.checkMathML function in jqmath-0.1.js for actual code. It is complicated a bit by trying to work with or without XML namespaces (depending on the browser), and allowing for a namespace prefix for the MathPlayer plugin for Internet Explorer.

Answer 3

With Element#getBoundingClientRect

function hasMathMLSupport() {
  const div = document.createElement("div");
  div.innerHTML = '<math><mfrac><mn>1</mn><mn>2</mn></mfrac></math>' +
                  '<math><mn>1</mn></math>';
  document.body.appendChild(div);
  return div.firstElementChild.firstElementChild.getBoundingClientRect().height > div.lastElementChild.firstElementChild.getBoundingClientRect().height + 1;
}

console.log(hasMathMLSupport());

With window.getComputedStyle

(does not work in Mi Browser in Night Mode as it changes color to rgba(255, 255, 255, 0.5))

function hasMathMLSupport() {
  const div = document.createElement("div");
  div.innerHTML = '<math><mrow mathcolor=\"red\"><mn>1</mn></mrow></math>';
  document.body.appendChild(div);
  return window.getComputedStyle(div.firstChild.firstChild, null).color === "rgb(255, 0, 0)";
}

console.log(hasMathMLSupport());

With Element.querySelector(":link"): (Safari 10+, Firefox ?+)

function hasMathMLSupport() {
  const div = document.createElement("div");
  div.innerHTML = '<math><mrow href=\"https://ya.ru\"><mn>1</mn></mrow></math>';
  document.body.appendChild(div);
  return !!div.querySelector(":link");
}

console.log(hasMathMLSupport());

With window.MathMLElement != null (the interface was added in MathML 4 spec)

Answer 4

This still does not seem to be straight forward.

http://www.w3.org/TR/MathML2/chapter8.html

Support for the MathML Document Object Model may be queried by calling the DOMImplementation::hasFeature method with the test string "org.w3c.dom.mathml"

This implies a simple test however Chrome and IE support this through plug ins, but Chrome returns true even when it has no plug-in

My solution is to use the w3c spec but correct for cases where the browser [chrome] has to opposite response. Then I can use MathJax if necessary, which is always, except for firefox. The script goes in the html < head > section

<script type="text/javascript">

  //Browser detector for Chrome
  //returns true if the Browser is Chrome
  function isChrome(){
    var regex = /Chrome\/[0-9]{1,2}\.[0-9]/
    var matches = navigator.userAgent.match(regex)
    //console.log( matches )
    return (matches!=null && matches.length==1)
  }

  /*
   *  Feature Detect for MathML as w3c specification
   *  <returns>boolean: true if mathML is supported in browser
   */
  function hasFeatureMathML(){
    MATHML_FEATURE = "org.w3c.dom.mathml"     //as per w3c specification
    MATHML_FEATURE_VERSION = "2.0"            //Any version number appears to work
    if(isChrome()) return false               //Opps Chrome not natively supported yet
    return document.implementation.hasFeature(MATHML_FEATURE, MATHML_FEATURE_VERSION )
  }

  /*
   * init MathML use MathJax according to
   *     http://docs.mathjax.org/en/latest/dynamic.html
   * with additional test to confirm necessity
   * <returns>boolean: true if mathML is supported in browser
   */
  function initMathML(){
    var script = document.createElement("script");
    script.type = "text/javascript";
    script.src  = "http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML";

    //doctorBob added test on next line, return if has native support for MathML
    if( hasFeatureMathML() ) return true

    document.getElementsByTagName("head")[0].appendChild(script)
    return false
  }

  //initialize in html <head> incase MathJax is required
  var browserHasMathML = initMathML()
  if( !browserHasMathML )console.log("No Native MathML using MathJax")

</script>

I didn't really look into installing the browser plugins, because not everyone has them installed. This works in IE 8, Chrome 39, Firefox 38, Komodo Edit 6