jQuery源码分析--继承方法

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" && !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;

jQuery是使用了 sizzle的插件的，