JQuery的深拷贝和浅拷贝源码赏析

jQuery.extend = jQuery.fn.extend = function() {
var options, name, src, copy, copyIsArray, clone,
    target = arguments[ 0 ] || {},
    i = 1,
    length = arguments.length,
    deep = false;

// Handle a deep copy situation
if ( typeof target === "boolean" ) {
    deep = target;

    // Skip the boolean and the target
    target = arguments[ i ] || {};
    i++;
}

// Handle case when target is a string or something (possible in deep copy)
if ( typeof target !== "object" && !jQuery.isFunction( target ) ) {
    target = {};
}

// Extend jQuery itself if only one argument is passed
if ( i === length ) {
    target = this;
    i--;
}

for ( ; i < length; i++ ) {

    // Only deal with non-null/undefined values
    if ( ( options = arguments[ i ] ) != null ) {

        // Extend the base object
        for ( name in options ) {
            src = target[ name ];
            copy = options[ name ];

            // Prevent never-ending loop
            if ( target === copy ) {
                continue;
            }

            // Recurse if we're merging plain objects or arrays
            if ( deep && copy && ( jQuery.isPlainObject( copy ) || ( copyIsArray = Array.isArray( copy ) ) ) ) {

                if ( copyIsArray ) {
                    copyIsArray = false;
                    clone = src && Array.isArray( src ) ? src : [];

                } else {
                    clone = src && jQuery.isPlainObject( src ) ? src : {};
                }

                // Never move original objects, clone them
                target[ name ] = jQuery.extend( deep, clone, copy );

            // Don't bring in undefined values
            } else if ( copy !== undefined ) {
                target[ name ] = copy;
            }
        }
    }
}
// Return the modified object
return target;
};