Javascript add extra argument

Question

Lets take a look at this code:

var mainFunction = function() {
  altFunction.apply(null, arguments);
}

The arguments that are passed to \"mainF

Answer 1

The arguments object isn't an array; it's like an array, but it's different. You can turn it into an array however:

var mainArguments = [].slice.call(arguments, 0);

Then you can push another value onto the end:

mainArguments.push("whatever");

Answer 2

var myABC = '12321'; someFunction(result, error, myCallback.bind(this, myABC));

Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind

Answer 3

Use Array.prototype.push

[].push.call(arguments, "new value");

---

There's no need to shallow clone the arguments object because it and its .length are mutable.

(function() {
    console.log(arguments[arguments.length - 1]); // foo

    [].push.call(arguments, "bar");

    console.log(arguments[arguments.length - 1]); // bar
})("foo");

---

From ECMAScript 5, 10.6 Arguments Object

7. Call the [[DefineOwnProperty]] internal method on obj passing "length", the Property Descriptor {[[Value]]: len, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true}, and false as arguments.

So you can see that .length is writeable, so it will update with Array methods.

Answer 4

//
//    var
//        altFn  = function () {}, 
//        mainFn = prefilled( altFn  /* ...params */ );
//
//    mainFn(  /* ...params */  );
//  
//        
function prefilled ( fn /* ...params */ ) { 
     return ( function ( args1 ) { 

          var orfn = this;

          return function () { 

              return orfn.apply( this, args1.concat( cslc( arguments ) ) );

          };

     } ).call( fn, cslc( arguments, 1 ) );
}

// helper fn
function cslc( args, i, j ) { 
   return Array.prototype.slice.call( args, i, j );
}


// example

var
    f1 = function () { console.log( cslc( arguments ) ); }, 
    F1 = prefilled( f1, 98, 99, 100 );

F1( 'a', 'b', 'c' );

//
//   logs: [98, 99, 100, "a", "b", "c"]
//
//

Answer 5

In this case it could be more comfortable to use call() instead of apply():

function first(parameter1, parameter2) {

  var parameter3 = "123";

  secondFunction.call(
    this,
    parameter1,
    parameter2,
    parameter3);
},

Answer 6

arguments is not a pure array. You need to make a normal array out of it:

var mainArguments = Array.prototype.slice.call(arguments);
mainArguments.push("extra data");