Inject a snippet of JavaScript into the page for execution in the context of the currently selected frame. The executed script is assumed to be synchronous.
The script argument defines the script to execute in the form of a function body. The value returned by that function will be returned to the client.

The function will be invoked with the provided args array and the values may be accessed via the arguments object in the order specified.

Under the hood, if the body param is a function it is converted to a string with function.toString(). Any references to your current scope are ignored.

To ensure cross-browser compatibility, the specified function should not be in ES6 format (i.e. () => {}). If the execution of the function fails, the first argument of the callback contains error information.

Usage:

Parameters:

Name Type description
body string|function

The function body to be injected.

args Array

An array of arguments which will be passed to the function.

callback
Optional
function

Optional callback function to be called when the command finishes.

Returns:

Type description
* The script result.

Example:

 this.demoTest = function (browser) {
   browser.executeScript(function(imageData) {
     // resize operation
     return true;
   }, [imageData], function(result) {
     // result.value === true
   });
}

W3C WebDriver spec: