HTML5 MathML
HTML5 MathML selection Attribute
The selection attribute on <maction> chooses which of its child expressions is currently displayed, identified by a 1-based index.
Definition and usage
The selection attribute holds a positive integer that indexes the children of an <maction> element, starting at 1. It sets which child is shown; with actiontype="toggle", it also marks the starting point for cycling.
Which elements use it
- <maction> - selects the displayed child by 1-based index.
Example
<math>
<maction actiontype="toggle" selection="2">
<mn>0.5</mn>
<mfrac><mn>1</mn><mn>2</mn></mfrac>
</maction>
</math>With selection="2", the fraction (the second child) is displayed initially instead of the decimal.
⚠️
Because <maction> is not required by MathML Core, browsers typically just render the selected child and ignore any toggling; the selection value still determines what is shown.