Executes JavaScript in the window that the devtools are attached to.
This is somewhat like using
tabs.executeScript()
to attach a content script, but with two main differences:
First, the JavaScript can use a set of special commands that browsers typically provide in their devtools console implementation : for example, using "$0" to refer to the element currently selected in the Inspector.
Second, the JavaScript you execute can see any changes made to the page by scripts that the page loaded. This is in contrast to content scripts, which see the page
as it would exist if no page scripts were loaded
. However, note that the isolation provided by content scripts is a deliberate security feature, intended to make it harder for malicious or uncooperative web pages to confuse or subvert WebExtensions APIs by redefining DOM functions and properties. This means you need to be very careful if you waive this protection by using
eval()
, and should use content scripts unless you need to use
eval()
.
The script is evaluated by default in the main frame of the page. The script must evaluate to a value that can be represented as JSON (meaning that, for example, it may not evaluate to a function or an object that contains any functions). By default, the script does not see any content scripts attached to the page.
You can't call
eval()
on privileged browser windows such as "about:addons".
You can optionally provide an
选项
parameter, which includes options to evaluate the script in a different frame or in the context of attached content scripts. Note that Firefox does not yet support the
选项
参数。
eval()
函数返回
Promise
that resolves to the evaluated result of the script or to an error.
The script gets access to a number of objects that help the injected script interact with the developer tools. The following helpers are currently supported:
$0
Contains a reference to the element that's currently selected in the devtools Inspector.
inspect()
Given an object, if it is an DOM element in the page, selects it in the devtools Inspector, otherwise it creates an object preview in the webconsole.
var evaluating = browser.devtools.inspectedWindow.eval(
expression, // string
options // object
)
表达式
string
. The JavaScript expression to evaluate. The string must evaluate to a object that can be represented as JSON, or an exception will be thrown. For example,
表达式
must not evaluate to a function.
选项
可选
对象
. Options for the function (Note that Firefox does not yet support this options), as follows:
frameURL
可选
string
. The URL of the frame in which to evaluate the expression. If this is omitted, the expression is evaluated in the main frame of the window.
useContentScriptContext
可选
boolean
。若
true
, evaluate the expression in the context of any content scripts that this extension has attached to the page. If you set this option, then you must have actually attached some content scripts to the page, or a Devtools error will be thrown.
contextSecurityOrigin
可选
string
. Evaluate the expression in the context of a content script attached by a different extension, whose origin matches the value given here. This overrides
useContentScriptContext
.
A
Promise
that will be fulfilled with an
array
containing two elements.
If no error occurred, element 0 will contain the result of evaluating the expression, and element 1 will be
undefined
.
If an error occurred, element 0 will be
undefined
, and element 1 will contain an object giving details about the error. Two different sorts of errors are distinguished:
isException
, set to
true
value
, giving more details.
isError
, set to
true
code
containing an error code.
BCD tables only load in the browser
This tests whether jQuery is defined in the inspected window, and logs the result. Note that this wouldn't work in a content script, because even if jQuery were defined, the content script would not see it.
function handleError(error) {
if (error.isError) {
console.log(`Devtools error: ${error.code}`);
} else {
console.log(`JavaScript error: ${error.value}`);
}
}
function handleResult(result) {
console.log(result);
if (result[0] !== undefined) {
console.log(`jQuery: ${result[0]}`);
} else if (result[1]) {
handleError(result[1]);
}
}
const checkjQuery = "typeof jQuery != 'undefined'";
evalButton.addEventListener("click", () => {
browser.devtools.inspectedWindow.eval(checkjQuery)
.then(handleResult);
});
This uses the
$0
helper to set the background color of the element that's currently selected in the Inspector:
const evalButton = document.querySelector("#reddinate");
const evalString = "$0.style.backgroundColor = 'red'";
function handleError(error) {
if (error.isError) {
console.log(`Devtools error: ${error.code}`);
} else {
console.log(`JavaScript error: ${error.value}`);
}
}
function handleResult(result) {
if (result[1]) {
handleError(result[1]);
}
}
evalButton.addEventListener("click", () => {
browser.devtools.inspectedWindow.eval(evalString)
.then(handleResult);
});
This uses the
inspect()
helper to select the first <h1> element in the page:
const inspectButton = document.querySelector("#inspect");
const inspectString = "inspect(document.querySelector('h1'))";
function handleError(error) {
if (error.isError) {
console.log(`Devtools error: ${error.code}`);
} else {
console.log(`JavaScript error: ${error.value}`);
}
}
function handleResult(result) {
if (result[1]) {
handleError(result[1]);
}
}
inspectButton.addEventListener("click", () => {
browser.devtools.inspectedWindow.eval(inspectString)
.then(handleResult);
});
注意：
This API is based on Chromium's
chrome.devtools
API。
Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.
最后修改： , 由 MDN 贡献者