custom-array-like-object.js

var array_like = {};

array_like[ 0 ] = "test 0";
array_like[ 1 ] = "test 1";
array_like[ 2 ] = "test 2";
array_like[ 3 ] = "test 3";

array_like.length = 4;
array_like.splice = [].splice;

console.log( array_like );
console.log( $.type( array_like ) );
console.log( array_like[ 2 ] );

jquery-array-like-object.js

var $nodes = $( "div" ),
    node = $nodes[ 2 ];

console.log( $nodes );
console.log( $.type( $nodes ) );
console.log( node );

jquery-internal-object-array-merge.js

// ... more code ...
merge: function( first, second ) {
    var l = second.length,
        i = first.length,
        j = 0;

    if ( typeof l === "number" ) {
        for ( ; j < l; j++ ) {
            first[ i++ ] = second[ j ];
        }
    } else {
        while ( second[j] !== undefined ) {
            first[ i++ ] = second[ j++ ];
        }
    }

    first.length = i;

    return first;
},
// ... more code ...