devtools.panels.ElementsPanel.setExpression()

Evaluates an expression in the context of the inspected page, and displays the result in the extension sidebar pane.

The expression's execution context is the same as that for inspectedWindow.eval().

JSON objects and DOM nodes are displayed as an expandable tree, as in the JSON viewer in Firefox. You can optionally specify a rootTitle string: this will be displayed as the title of the tree's root.

This is an asynchronous function that returns a Promise.

Syntax

let evaluating = browser.devtools.panels.setExpression(
  expression,       // string
  rootTitle         // string
)

Parameters

expression: string. The expression to evaluate.
rootTitle Optional: string. The title of the root of the tree in which results are displayed.

Return value

A Promise that will be fulfilled with no arguments, once the expression has been evaluated.

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`setExpression`	Yes The expression must evaluate to a JavaScript object or a DOM node, or nothing is shown in the sidebar.	79 The expression must evaluate to a JavaScript object or a DOM node, or nothing is shown in the sidebar.	57 The expression must evaluate to an object that can be serialized to JSON, or nothing is shown in the sidebar. In particular, JavaScript cyclic objects and DOM nodes are not supported. See bug 1403130.	?	Yes	No	?	?	No	?	No	?

Examples

This code creates a sidebar pane that displays the tagName of the currently selected element:

function onCreated(sidebarPane) {

  browser.devtools.panels.elements.onSelectionChanged.addListener(() => {
    const exp = "$0 && $0.tagName";
    const title = "Selected Element tagName";
    sidebarPane.setExpression(exp, title);
  });

}

browser.devtools.panels.elements.createSidebarPane("My pane").then(onCreated);

Note: This API is based on Chromium's chrome.devtools.panels API.

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/devtools/panels/ExtensionSidebarPane/setExpression