jquery代码阅读jQuery.makeArray()

jquery的makeArray 函数可以将一个类数组对象转成数组，官方API解释和测试例子在这里（Convert
an array-like object into a true JavaScript array.）那么什么是类数组对象呢？（ array-like object ）
这是Arrary-Like的定义

Array-Like Object

Either a true JavaScript Array or a JavaScript Object that contains a nonnegative integer

length

property
and index properties from

0

up to

length
- 1

. This latter case includes array-like objects commonly encountered in web-based code such as the

arguments

object
and the

NodeList

object returned by many DOM methods.

When a jQuery API accepts either plain Objects or Array-Like objects, a plain Object with a numeric

length

property
will trigger the Array-Like behavior.

含有length属性，并且值不为负数，能够按照下标访问属性。常见的类数组对象有aruments，NodeList

// results is for internal usage only result是jquery内部使用的参数，如果不为空则把array并到resuls上
makeArray: function( array, results ) {
var ret = results || [];

if ( array != null ) {
// The window, strings (and functions) also have 'length'
// Tweaked logic slightly to handle Blackberry 4.7 RegExp issues #6930
var type = jQuery.type( array );
//array没有length属性，或者为string类型，function类型，window类型，或者黑莓中正则对象，黑莓中正则对象也含有length对象，则push到result
if ( array.length == null || type === "string" || type === "function" || type === "regexp" || jQuery.isWindow( array ) ) {
push.call( ret, array );
} else {
//调用merge把类数组array合并到ret
jQuery.merge( ret, array );
}
}

return ret;
}

其中调用的jquery.type 在这里

jquery.isWindow() 1.7.1是根据是否包含setInterval属性来判断的"setInterval" in obj，而以后版面是通过window属性来判断的obj == obj.window

isWindow:function(obj){
return obj && typeof obj === "object" && "setInterval" in obj;
//1.7.2: return obj != null && obj == obj.window;
},

调用的jQuery.merge(frist,second) 官方解释在这里 ，该函数的作用是把第二个数组或类数组对象合并到第一个中去

merge: function( first, second ) {
var i = first.length,
j = 0;
//length属性为数字，则把second当做数组处理，没有length属性或者不为数字当做含有连续整型的属性对象处理{0:"HK",1:"CA"}
if ( typeof second.length === "number" ) {
for ( var l = second.length; j < l; j++ ) {
first[ i++ ] = second[ j ];
}

} else {
while ( second[j] !== undefined ) { //把不为undefined的都合并到first中
first[ i++ ] = second[ j++ ];
}
}

first.length = i; //修正length属性，fisrt可能不为真正的数组类型

return first;
},