Execute Javascript in iOS Applications

In this tutorial, I have covered How to execute JavaScript in iOS / Objective-C. You can execute JavaScript in iOS applications with the help of JavaScriptCore.framework. This framework is supported in iOS7 & OSX 10.9

List of features supported by Javascript.framework
a) Evaluate JavaScript code in Objective-C
b) Access JavaScript Variables in Objective-C
c) Access JavaScript functions and execute them in Objective-C
d) Execute Objective-C code from JavaScript
e) Export Objective-C classes and use them in JavaScript.

Download the source code: 

To access JavaScript framework, you need to include the header file

#import <JavaScriptCore/JavaScriptCore.h>

List of Main Classes supported by framework:
JSContext : For any javascript operations you need JSContext.

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

JSValue : JSValue holds JavaScript values,variables and functions. List of main methods in JSValue.

// Convert this value to a corresponding Objective-C object, according to the
// conversion specified above.
- ( id )toObject;

// Convert this value to a corresponding Objective-C object, if the result is
// not of the specified class then nil will be returned.
- ( id )toObjectOfClass:(Class)expectedClass;

// The value is copied to a boolean according to the conversion specified by the
// JavaScript language.
- ( BOOL )toBool;

// The value is copied to a number according to the conversion specified by the
// JavaScript language.
- ( double )toDouble;

// The value is copied to an integer according to the conversion specified by
// the JavaScript language.
- (int 3 2 _t)toInt 3 2 ;

// The value is copied to an integer according to the conversion specified by
// the JavaScript language.
- (uint 3 2 _t)toUInt 3 2 ;

// If the value is a boolean, a NSNumber value of @YES or @NO will be returned.
// For all other types the value will be copied to a number according to the
// conversion specified by the JavaScript language.
- ( NSNumber *)toNumber;

// The value is copied to a string according to the conversion specified by the
// JavaScript language.
- ( NSString *)toString;

// The value is converted to a number representing a time interval since 1970,
// and a new NSDate instance is returned.
- ( NSDate *)toDate;

// If the value is null or undefined then nil is returned.
// If the value is not an object then a JavaScript TypeError will be thrown.
// The property "length" is read from the object, converted to an unsigned
// integer, and an NSArray of this size is allocated. Properties corresponding
// to indicies within the array bounds will be copied to the array, with
// Objective-C objects converted to equivalent JSValues as specified.
- ( NSArray *)toArray;

// If the value is null or undefined then nil is returned.
// If the value is not an object then a JavaScript TypeError will be thrown.
// All enumerable properties of the object are copied to the dictionary, with
// Objective-C objects converted to equivalent JSValues as specified.
- ( NSDictionary *)toDictionary;

 

Accessing Javascript Code in Objective-C

1).Evaluating Javascript Code

NSString * jsCode = @"1+2" ;
JSContext *context = [[ JSContext alloc ] init ];
JSValue * value = [context evaluateScript :jsCode];
NSLog( @"Output = %d" , [value toInt32 ]);

 

2).Access Javascript Variables. Variables and functions are accessed from JSContext.
To access varible from Javascript : context[@"x"]
To access function from javascript : context[@"myfun"]

JSContext *context = [[ JSContext alloc ] init ];
    NSString * jsCode = @"var x; x=10;" ;
    [context evaluateScript :jsCode];

    JSValue * a =context[ @"x" ];
    NSLog( @"x = %d" , [a toInt32 ]);

 

3).Access Javascript functions and execute them in Objective-C

//function with arguments
    JSContext *context = [[ JSContext alloc ] init ];
    NSString * jsCode = @"function sum(a,b) { return a+b;} " ;
    [context evaluateScript :jsCode];

    JSValue * func =context[ @"sum" ];
    NSArray * args = @[[ NSNumber numberWithInt : 1 0 ],[ NSNumber numberWithInt : 2 0 ]];
    JSValue * ret =[func callWithArguments :args];
    NSLog( @"10+20 = %d" , [ret toInt32 ]);

    //function without arguments
    NSString * jsCode 2 = @"function getRandom() { return parseInt(Math.floor((Math.random()*100)+1));} " ;
    [context evaluateScript :jsCode 2 ];

    JSValue * func 2 =context[ @"getRandom" ];

    for ( int i= 0 ;i< 5 ;i++)
    {
        JSValue * ret 2 =[func 2 callWithArguments :nil ];
        NSLog( @"Random Value = %d" , [ret 2 toInt32 ]);
    }

 

Call Objective-C code from JavaScript

Objective-C code is called from JavaScript in two ways

1.CODE BLOCKS

Objective-C code block can be called from JavaScript.

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

    //we are telling that "sum" is function, takes two arguments
    context[ @"sum" ] = ^( int arg 1 , int arg 2 )
    {
        return arg 1 +arg 2 ;
    };

    NSString * jsCode = @"sum(4,5);" ;
    JSValue * sumVal = [context evaluateScript :jsCode];

    NSLog( @"Sum(4,5) = %d" , [sumVal toInt32 ]);

    //we are telling that "getRandom" is function, does not take any arguments
    context[ @"getRandom" ] = ^()
    {
        return rand()% 1 0 0 ;
    };

    NSString * jsCode 2 = @"getRandom();" ;
    for ( int i= 0 ;i< 5 ;i++)
    {
        JSValue * sumVal 2 = [context evaluateScript :jsCode 2 ];
        NSLog( @"Random Number = %d" , [sumVal 2 toInt32 ]);
    }

 

2.USING JSEXPORT PROTOCOL

You can see the comparison between Objective-C Object and it’s equivalent Javascript Object below.

@interface MyObject @property int x; -( int ) getX; +( MyObject *) getSqure :(MyObject*)obj; @end //Usage: MyObject * obj = [ MyObject new ]; [obj getX ]; [ MyObject getSqure :obj];

function MyObject() { //member variable this .x=0; //instance method this .getX = function () { return this .x; } } //static method MyObject.getSqure = function (obj) { var newObj = new MyObject(); newObj.x = obj.x * obj.x; return newObj; } //Usage: var obj = new MyObject(); obj.x=10; var sqrObj = MyObject.getSqure(obj);

To make Javascript interacting with Objective-C Object, We need to have a Protocol which should be inherited
from JSExport. Move all the variables and functions to prototype to access them in JavaScript.

@protocol MyObjectExport
@property  int x;

-( int ) getX;
+( MyObject *) getSqure :(MyObject*)obj;

@end

@interface MyObject : NSObject <MyObjectExport>

//this method is not accessible in javascript
-( void ) test;

@end ;

@implementation MyObject
@synthesize x;

-( int ) getX
{
    return self .x ;
}
+( MyObject *) getSqure :(MyObject*)obj;
{
    NSLog( @"Calling getSqure" );
    MyObject * newObj = [ MyObject new ];
    newObj .x = obj .x * obj .x ;

    return  newObj;
}

Now MyObject(Objective-C)’s variables and functions are directly accessed from javascript.

JSContext * context = [[ JSContext alloc ] init ];
NSString * jsCode = @"function sqrtOf(obj){ return MyObject.getSqure(obj);}" ;

    //adding Objective-C Class to Javascript.
    context[ @"MyObject" ]=[ MyObject class ];

    [context evaluateScript :jsCode];

    MyObject * obj =[ MyObject new ];
    obj .x = 1 0 ;

    JSValue * func =context[ @"sqrtOf" ];
    JSValue * val = [func callWithArguments :@[obj]];

    //we got MyObject from javascript.
    MyObject *sqrtObj = [val toObject ];

    NSLog( @"Value =%d, %d" , obj .x , [sqrtObj getX ]);

 

转：http://hayageek.com/execute-javascript-in-ios/