Compatibility and error-prone issues that easily occur in js

The editor below will share with you an article summarizing some compatibility and error-prone issues in js. It has a good reference value and I hope it will be helpful to everyone. Let’s follow the editor and take a look.

1. Attribute related

We usually refer to attributes and properties collectively as Attributes, but they are indeed different concepts.

Features (attributes) will appear in HTML text, modifications to attributes will definitely appear in the element's outerHTML, and attributes only exist in element nodes;

Attributes (property) modify JS objects. Except for some built-in features of the browser, other attribute operations will not affect HTML text.

1. IE6/7 does not distinguish between attributes and characteristics

Other browsers will distinguish between attributes and characteristics, but IE67 does not distinguish between them. Under IE67 we only Features can be deleted using attribute names. Although these two names are often the same, there are always differences.

2. IE6/7 cannot use getAttribute/setAttribute to operate features whose values ​​are not strings

In modern browsers, getAttribute will definitely return the corresponding value in HTML String, and the result returned by IE67 is unpredictable, so under IE67, we need to use AttributeNode to operate attributes.

3. IE6/7/8 cannot obtain CSS text through the style attribute

This problem should be the sequelae of IE6/7 not distinguishing between attributes and characteristics. When using the style attribute, just use elem.style.cssText.

4. IE6/7 will parse relative URLs into absolute URLs

This problem even causes the empty src attribute under IE6/7 to generate repeated requests. You can Use getAttribute('href/src', 4).

5. The default behavior of element characteristics is different

There will be many bugs of this type. For example, in some old webkit browsers, the default behavior of checkbox/radio The value is "", not on. In some older webkit browsers the first element of the select will not be selected.

2. Style operations

Normally, styles include getting and setting inline styles and getting the calculated styles of elements

1. IE supports background-position-x/y but other browsers do not.

background-position-x/y can be used to conveniently gradient the position of an image. If it is not supported, we can consider using the parsing background-position attribute to handle it.

2. IE6/7 does not support the opacity attribute

You can achieve the same effect through the alpha filter, but remember to trigger the haslayout of the element.

3. IE6/7/8 will mistakenly let the nodes generated by clone inherit some attributes

For example, background, if you modify one or two, they will be changed at the same time.

4. Different ways to get the calculated style

IE6/7/8 uses elem.currentStyle while other browsers use the window.getComputedStyle function.

5. Different pixelation methods

Pixelization refers to converting distances whose units are not pixels into pixels to facilitate calculations. Strictly speaking this is not a compatibility issue, but it may be used across the board. In IE6/7/8, we can use elem.runtimeStyle with pixelLeft for processing.

Modern browsers can use the width attribute.

6. Some BUG behaviors when obtaining CSS

In the Webkti core browser, margin-right often goes wrong.

3. Query operation

Query passing refers to finding a set of elements through some characteristic strings, or judging whether the elements satisfy string.

1. IE6/7 does not distinguish between id and name

When using getElementById and getElementsByName under IE6/7, it will return the same id or name as the given value at the same time. element. Since the name is usually agreed upon by the backend, when we write JS, we should ensure that the id does not duplicate the name.

2. IE6/7 does not support getElementsByClassName and querySelectorAll

These two functions are supported from IE8, so under IE6/7, we can actually use them Only getElementByTagName.

3. IE6/7 does not support getElementsByTagName('*') and will return non-element nodes

Either do not use *, or write a function to filter it yourself.

4. querySelectorAll under IE8 is not friendly to attribute selectors

Almost all browser predefined attributes have problems. Try to use custom attributes or no attributes. Selector.

5. querySelectorAll does not support pseudo-classes under IE8

Sometimes pseudo-classes are very useful, but IE8 does not support them. jquery provides :first, :last, :even, :odd, :eq, :nth, :lt, :gt are not pseudo-classes, and we should not use them at any time.

6. The matches function of IE9 cannot handle elements that are not on the DOM tree

As long as the element is not on the DOM tree, it will definitely return false. It is really impossible to throw the element in Delete it after matching in the body. Of course, we can also write our own matching function to avoid backflow.

4. Event operations

Usually when people ask about the compatibility of JS, the first reaction will be attachEvent and addEventListener, but there are still many details about the difference between these two functions.

1. Event action objects are different

addEventListener is the current object to which the event bubbles up, while attachEvent is window.

. Event parameter objects are different

Be sure to note that the function bound to attachEvent has parameter e. Do not write e = e || event, but there are many parameter attributes of the two. Differences, such as button or witch, whether pageY is supported or not, etc.

2. The evil wheel event

The support for wheel events is a mess, the rules are as follows:
IE6-11 chrome mousewheel wheelDetla down-120 up 120

firefox DOMMouseScroll detail next 3 upper-3

firefox wheel detlaY next 3 upper-3

IE9-11 wheel deltaY next 40 upper-40

chrome wheel deltaY Next 100 Up -100

3. Three major non-bubbling events

The focus/blur events of all browsers do not bubble. Fortunately, most of them do not bubble. Some browsers support focusin/focusout events, but the damn Firefox doesn't even support this.

The submit event does not bubble under IE678.

Under IE678, the change event will not be triggered until blur.

We have no effective means to solve these three problems and can only deal with them through simulation triggering.

4. a.click()

This method is unsafe in many browsers. Once executed, even if the default behavior is blocked, the page will still jump. .

5. Node operation

Node operation usually refers to copying, generating a node or moving the location of a node.

1.. innerHTML

When using innerHTML in IE6/7/8, there must be a text node in front, otherwise many tags will be lost. In addition, in many cases, using innerHTML will cause errors in the defaultValue attribute.

2. Useless tbody

IE6/7/8 will automatically add an empty tbody to an empty table

3. When cloningNode, the attachEvent event

will be copied and unless we record the events we bound, we cannot unbind them.

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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