Objective-C

NSString *str = CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(NULL, (__bridge CFStringRef)someStringToEncode, NULL, (__bridge CFStringRef)@"!*'\"();:@&=+$,/?%[]% ", CFStringConvertNSStringEncodingToEncoding(NSUTF8StringEncoding)));

JavaScript

var str = encodeURIComponent(str);