1、jquery.extend()
/**
* extend()方法是挂载到jQuery和jQuery原型上的方法:
* 我们可以通过下面两种方式调用:
* (1): $.extend();
* (2): $.fn.extend();
*/
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" && !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 ) {
copy = options[ name ];
// Prevent Object.prototype pollution
// Prevent never-ending loop
if ( name === "__proto__" || target === copy ) {
continue;
}
// Recurse if we're merging plain objects or arrays
if ( deep && copy && ( jQuery.isPlainObject( copy ) ||
( copyIsArray = Array.isArray( copy ) ) ) ) {
src = target[ name ];
// Ensure proper type for the source value
if ( copyIsArray && !Array.isArray( src ) ) {
clone = [];
} else if ( !copyIsArray && !jQuery.isPlainObject( src ) ) {
clone = {};
} else {
clone = src;
}
copyIsArray = false;
// 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;
};
2、extend()方法两种调用方式的区别:
/**
* 1、通过 $.extend()调用是把jQuery当做一个普通对象来用,
* 是向jQuery这个普通对象身上扩展方法,这种用法一般是
* 为了完善类库,提供更多的工具方法;扩展到jQuery对象上;
*
* 2、通过$.fn.extend()调用是把jQuery当做构造函数来用,
* 这样用一般是为了写插件,让jQuery的实例来调用;
* 这时是扩展到jQuery构造函数的原型上;
*/
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