Changing button text onclick

Question

When I click on myButton1 button, I want the value to change to Close Curtain from Open Curtain.
HTML:

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Answer 1

Or more simple without having to name the element (with 'button' element):

Stop logs

and script :

var bWriteLog = true;

function toggleLog(elt) {

  bWriteLog = !bWriteLog;
  elt.innerHTML = bWriteLog ? 'Stop logs' : 'Watch logs';
}