参考：

[_webView stringByEvaluatingJavaScriptFromString:@"methodName();"];

NSString* returnValue =[theWebView stringByEvaluatingJavaScriptFromString:@"myFunction('pass your parameter')"];

One can use JavaScriptCore framework to run JavaScript code from Objective-C.

#import <JavaScriptCore/JavaScriptCore.h>

JSContext *context = [[JSContext alloc] init];

[context evaluateScript: @"function greet(name){ return 'Hello, ' + name; }"];

JSValue *function = context[@"greet"];

JSValue* result = [function callWithArguments:@[@"World"]];

[result toString]; // -> Hello, World

Here is a demo: