如何在纯 JavaScript 中获取 div 的边距值？

Question

I can get height in jQuery with

$(item).outerHeight(true);

but how do I with JS?

I can get the height of the li with

document.getElementById(item).offsetHeight

but i will always get "" when I try margin-top:

document.getElementById(item).style.marginTop

Answer 1

The properties on the style object are only the styles applied directly to the element (eg, via a style attribute or in code). So .style.marginTop will only have something in it if you have something specifically assigned to that element (not assigned via a style sheet, etc.).

To get the current calculated style of the object, you use either the currentStyle property (Microsoft) or the getComputedStyle function (pretty much everyone else).

Example:

var p = document.getElementById("target");
var style = p.currentStyle || window.getComputedStyle(p);

display("Current marginTop: " + style.marginTop);

Fair warning: What you get back may not be in pixels. For instance, if I run the above on a p element in IE9, I get back "1em" .

Live Copy | Source

Answer 2

Also, you can create your own outerHeight for HTML elements. I don't know if it works in IE, but it works in Chrome. Perhaps, you can enhance the code below using currentStyle , suggested in the answer above.

Object.defineProperty(Element.prototype, 'outerHeight', {
    'get': function(){
        var height = this.clientHeight;
        var computedStyle = window.getComputedStyle(this); 
        height += parseInt(computedStyle.marginTop, 10);
        height += parseInt(computedStyle.marginBottom, 10);
        height += parseInt(computedStyle.borderTopWidth, 10);
        height += parseInt(computedStyle.borderBottomWidth, 10);
        return height;
    }
});

This piece of code allow you to do something like this:

document.getElementById('foo').outerHeight

According to caniuse.com, getComputedStyle is supported by main browsers (IE, Chrome, Firefox).

Answer 3

I found something very useful on this site when I was searching for an answer on this question. You can check it out at http://www.codingforums.com/javascript-programming/230503-how-get-margin-left-value.html . The part that helped me was the following:

 /*** * get live runtime value of an element's css style * http://robertnyman.com/2006/04/24/get-the-rendered-style-of-an-element * note: "styleName" is in CSS form (ie 'font-size', not 'fontSize'). ***/ var getStyle = function(e, styleName) { var styleValue = ""; if (document.defaultView && document.defaultView.getComputedStyle) { styleValue = document.defaultView.getComputedStyle(e, "").getPropertyValue(styleName); } else if (e.currentStyle) { styleName = styleName.replace(/\\-(\\w)/g, function(strMatch, p1) { return p1.toUpperCase(); }); styleValue = e.currentStyle[styleName]; } return styleValue; } //////////////////////////////////// var e = document.getElementById('yourElement'); var marLeft = getStyle(e, 'margin-left'); console.log(marLeft); // 10px

 #yourElement { margin-left: 10px; }

 <div id="yourElement"></div>

Answer 4

Here is my solution:

Step 1: Select the element

Step 2: Use getComputedStyle and provide the element to it

Step 3: Now access all the properties

const item = document.getElementbyId('your-element-id');
const style= getComputedStyle(item);
const itemTopmargin = style.marginTop;
console.log(itemTopmargin)

It will give you margin with px units like "16px" which you might not want. You can extract the value using parseInt()

const marginTopNumber = parseInt(itemTopmargin)
console.log(marginTopNumber)

It will give you the numerical value only (without any units).