There are many introductions about jQuery's this and $(this) on the Internet. Most of them just clarify the directions of this and $(this). In fact, they have applications and cannot be generalized. When jQuery calls member functions, this points to the dom object.
It is understandable that$(this) points to the jQuery object, but this points to the dom object. This is because jQuery has done special processing.
When creating a jQuery object of dom, jQuery not only creates a jQuery object for dom, but also stores dom in the array of the created object.
elem = document.getElementById(match[2]);
if (elem && elem.parentNode) {
This.length = 1;
this[0] = elem;
}
this.context = document;
this.selector = selector;
return this;
The statement this[0] = elem implements an object array. So JavaScript is a very interesting language. When using this to access, you can access the member functions of the object it points to, and in fact this is an array of objects. It stores dom objects.
Let’s take a look at $("p").each() -- loop
each: function( callback, args ) {
return jQuery.each( this, callback, args );
}
After reading the call of each function, you should understand that jQuery.each( this, callback, args ); calls an array of objects, and the array of objects stores dom objects, so this in the callback function is naturally dom Target
Look again at $("p").hide() --Member function
hide: function() {
return showHide( this );
},
function showHide( elements, show ) {var elem, display,
values = [],
index = 0,
length = elements.length;
for ( ; index elem = elements[ index ];
if ( !elem.style ) {
continue;
}
values[ index ] = jQuery._data( elem, "olddisplay" );
if ( show ) {
// Reset the inline display of this element to learn if it is
// being hidden by cascaded rules or not
if ( !values[ index ] && elem.style.display === "none" ) {
elem.style.display = "";
}
// Set elements which have been overridden with display: none
// in a stylesheet to whatever the default browser style is
// for such an element
if ( elem.style.display === "" && isHidden( elem ) ) {
values[ index ] = jQuery._data( elem, "olddisplay", css_defaultDisplay(elem.nodeName) );
}
} else {
display = curCSS( elem, "display" );
if ( !values[ index ] && display !== "none" ) {
jQuery._data( elem, "olddisplay", display );
}
}
}
// Set the display of most of the elements in a second loop
// to avoid the constant reflow
for ( index = 0; index elem = elements[ index ];
if ( !elem.style ) {
continue;
}
if ( !show || elem.style.display === "none" || elem.style.display === "" ) {
elem.style.display = show ? values[ index ] || "" : "none";
}
}
return elements;
}
从上面的代码可以看出hide行数其实调用的是showHide,而传入的第一个参数this,并不是dom对象,而是jQuery对象数组,因此showHide函数通过循环此对象数组获取每一个dom对象。
最后看看$("p").bind() -- 事件
bind: function( types, data, fn ) {
return this.on( types, null, data, fn );
},
on: function( types, selector, data, fn, /*INTERNAL*/ one ) {
// This part of the code is omitted
return this.each( function() { jQuery.event.add( this, types, fn, data, selector );
});
},

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