Use JavaScript getComputedStyle to get and set the principle of style _javascript tips

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The most interesting thing is to use JavaScript to get and set style

The DOM Standard introduces the concept of overriding stylesheets when we use document.getElementById ("id"). Style.backgroundcolor gets the style only when it gets the background color set in the Style property in the ID. If Background-color is not set in the style attribute in the ID, then it returns empty, that is, if the ID uses the class attribute to refer to an external style sheet, the background color set in the external style sheet, So sorry. document.getElementById ("id"). Style.backgroundcolor this is not the case, if you want to get the settings in the external style sheet, you need to use the Window object's getComputedStyle ( method, the code writes window.getComputedStyle (id,null). backgroundcolor
But the compatibility problem comes again, so write in Firefox, but not in IE
Two compatible ways to write
Window.getcomputedstyle?window.getcomputedstyle (id,null). backgroundcolor:id.currentstyle["BackgroundColor"];
If you get the background color, this method in Firefox and IE return value is not the same, IE is returned to the "#ffff99" appearance, and Firefox returned "RGB (238, 44, 34)"
It is noteworthy that: window.getComputedStyle (id,null) This way can not set the style, can only be obtained, to be set up to be written like this id.style.background= "#EE2C21";