W3Schools Tryit 编辑器 - W3Schools 中文教程

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<h1>The Storage Event</h1>

<p>The Storage event is triggered when there is a change in the window's storage area.</p>

<p><strong>Note:</strong> The storage event is only triggered when a window 
<strong>other than itself</strong> makes the changes.</p>

<p>Therefore, in this example, a new window is created, and the changes is done in the new window.</p>

<h1>The oldValue Property</h1>

<p>The oldValue property belongs to the Storage Event object, and returns the old value of the item that was changed.</p>

<button onclick="changeValue()">Change a Storage Item</button>

function myFunction(event) {
  var txt = "Key: " + event.key + "<br>";
  txt += "Old Value: " + event.oldValue + "<br>";
  txt += "New Value: " + event.newValue;
  document.getElementById("demo").innerHTML = txt;
}

function changeValue() {
  var x = window.open("", "myWindow", "width=200,height=100");
  x.localStorage.setItem("mytime", Date.now());
  x.close();
}
</script>
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