Example of Function Currying JavaScript - With Buster Specs

functionCurry.js

/**
* Curry function 
*/

function curryFn(a, b, c, x, y, z) {
    
    "use strict";
    
    var output = 1, args = [].slice.call(arguments),i,len, finalArgs;
    curryFn.__args = ( curryFn.__args || [] ).concat( args );
    if( curryFn.__args.length < curryFn.length ) {
        return curryFn;
    }
    finalArgs = curryFn.__args.slice( 0, curryFn.length );
    for (i = 0,len=finalArgs.length;i<len;i++) {
        output = output * finalArgs[i];
    }
    return output;
}

functionCurry.test.js

buster.spec.expose();

describe("Currying Function", function() {    
    
    before(function(){
        curryFn.__args = [];
    });
    
    it("should give output when called fn(a,b,c,x,y,z)", function() {
        var result = curryFn(13,45,21,78,9,57);
        expect( result ).toEqual(491571990);
    });
    
    it("should give output when called fn(a,b,c)(x,y,z)", function() {
        var result = curryFn(13,45,21)(78,9,57);
        expect( result ).toEqual(491571990);
    });
    
    it("should give output when called fn(a)(b)(c)(x)(y)(z)", function() {
        var result = curryFn(13)(45)(21)(78)(9)(57);
        expect( result ).toEqual(491571990);
    });
    
    it("should give output when called fn(a,b,c)(x)(y)(z)", function() {
        var result = curryFn(13,45,21)(78)(9)(57);
        expect( result ).toEqual(491571990);
    });
    
    it("should give output when called fn(a)(b)(c)(x,y,z)", function() {
        var result = curryFn(13)(45)(21)(78,9,57);
        expect( result ).toEqual(491571990);
    });
    
    it("should give output when called fn(a,b)(c,x)(y,z)", function() {
        var result = curryFn(13,45)(21,78)(9,57);
        expect( result ).toEqual(491571990);
    });
    
    it("should give output even if the number of arguments are more", function() {
        var result = curryFn(13,45)(21,78)(9,57,45,23,13);
        expect( result ).toEqual(491571990);
    });

});