[javascript] How do I get the information from a meta tag with JavaScript?

The information I need is in a meta tag. How can I access the "content" data of the meta tag when property="video"?

HTML:

<meta property="video" content="http://video.com/video33353.mp4" />

If you are interessted in a more far-reaching solution to get all meta tags you could use this piece of code

function getAllMetas() {
    var metas = document.getElementsByTagName('meta');
    var summary = [];
    Array.from(metas)
        .forEach((meta) => {
            var tempsum = {};
            var attributes = meta.getAttributeNames();
            attributes.forEach(function(attribute) {
                tempsum[attribute] = meta.getAttribute(attribute);
            });
            summary.push(tempsum);
        });
    return summary;
}

// usage
console.log(getAllMetas());

Here's a function that will return the content of any meta tag and will memoize the result, avoiding unnecessary querying of the DOM.

var getMetaContent = (function(){
        var metas = {};
        var metaGetter = function(metaName){
            var theMetaContent, wasDOMQueried = true;;
            if (metas[metaName]) {
                theMetaContent = metas[metaName];
                wasDOMQueried = false;
            }
            else {
                 Array.prototype.forEach.call(document.getElementsByTagName("meta"), function(el) {
                    if (el.name === metaName) theMetaContent = el.content;
                    metas[metaName] = theMetaContent;
                });
            }
            console.log("Q:wasDOMQueried? A:" + wasDOMQueried);
            return theMetaContent;
        }
        return metaGetter;
    })();

getMetaContent("description"); /* getMetaContent console.logs the content of the description metatag. If invoked a second time it confirms that the DOM  was only queried once */

And here's an extended version that also queries for open graph tags, and uses Array#some:

var getMetaContent = (function(){
        var metas = {};
        var metaGetter = function(metaName){
            wasDOMQueried = true;
            if (metas[metaName]) {
                wasDOMQueried = false;
            }
            else {
                 Array.prototype.some.call(document.getElementsByTagName("meta"), function(el) {
                        if(el.name === metaName){
                           metas[metaName] = el.content;
                           return true;
                        }
                        if(el.getAttribute("property") === metaName){
                           metas[metaName] = el.content;
                           return true;
                        }
                        else{
                          metas[metaName] = "meta tag not found";
                        }  
                    });
            }
            console.info("Q:wasDOMQueried? A:" + wasDOMQueried);
            console.info(metas);
            return metas[metaName];
        }
        return metaGetter;
    })();

getMetaContent("video"); // "http://video.com/video33353.mp4"

Way - [ 1 ]

function getMetaContent(property, name){
    return document.head.querySelector("["+property+"="+name+"]").content;
}
console.log(getMetaContent('name', 'csrf-token'));

You may get error: Uncaught TypeError: Cannot read property 'getAttribute' of null

Way - [ 2 ]

function getMetaContent(name){
    return document.getElementsByTagName('meta')[name].getAttribute("content");
}
console.log(getMetaContent('csrf-token'));

You may get error: Uncaught TypeError: Cannot read property 'getAttribute' of null

Way - [ 3 ]

function getMetaContent(name){
    name = document.getElementsByTagName('meta')[name];
    if(name != undefined){
        name = name.getAttribute("content");
        if(name != undefined){
            return name;
        }
    }
    return null;
}
console.log(getMetaContent('csrf-token'));

Instead getting error, you get null, that is good.

copy all meta values to a cache-object:

/* <meta name="video" content="some-video"> */

const meta = Array.from(document.querySelectorAll('meta[name]')).reduce((acc, meta) => (
  Object.assign(acc, { [meta.name]: meta.content })), {});

console.log(meta.video);

There is an easier way:

document.getElementsByName('name of metatag')[0].getAttribute('content')

FYI according to https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta global attributes are valid which means the id attribute can be used with getElementById.

In Jquery you can achieve this with:

$("meta[property='video']");

In JavaScript you can achieve this with:

document.getElementsByTagName('meta').item(property='video');

<html>
<head>
<meta property="video" content="http://video.com/video33353.mp4" />
<meta name="video" content="http://video.com/video33353.mp4" />
</head>
<body>

<script>
var meta = document.getElementsByTagName("meta");
    size = meta.length;

for(var i=0; i<size; i++) {
    if (meta[i].getAttribute("property") === "video") {
        alert(meta[i].getAttribute("content"));
    }
}
meta = document.getElementsByTagName("meta")["video"].getAttribute("content");
alert(meta);
</script>
</body>
</html>

Demo

if the meta tag is:

<meta name="url" content="www.google.com" />

JQuery will be:

const url = $('meta[name="url"]').attr('content'); // url = 'www.google.com'

JavaScript will be: (It will return whole HTML)

const metaHtml = document.getElementsByTagName('meta').url // metaHtml = '<meta name="url" content="www.google.com" />'

One liner here

document.querySelector("meta[property='og:image']").getAttribute("content");

function getMetaContentByName(name,content){
   var content = (content==null)?'content':content;
   return document.querySelector("meta[name='"+name+"']").getAttribute(content);
}

Used in this way:

getMetaContentByName("video");

The example on this page:

getMetaContentByName("twitter:domain");

Simple one, right?

document.head.querySelector("meta[property=video]").content

This code works for me

<meta name="text" property="text" content="This is text" />
<meta name="video" property="text" content="http://video.com/video33353.mp4" />

JS

var x = document.getElementsByTagName("META");
    var txt = "";
    var i;
    for (i = 0; i < x.length; i++) {
        if (x[i].name=="video")
        {
             alert(x[i].content);
         }

    }    

Example fiddle: http://jsfiddle.net/muthupandiant/ogfLwdwt/

The other answers should probably do the trick, but this one is simpler and does not require jQuery:

document.head.querySelector("[property~=video][content]").content;

The original question used an RDFa tag with a property="" attribute. For the normal HTML <meta name="" …> tags you could use something like:

document.querySelector('meta[name="description"]').content

function getDescription() {
    var info = document.getElementsByTagName('meta');
    return [].filter.call(info, function (val) {
        if(val.name === 'description') return val;
    })[0].content;
}

update version:

function getDesc() {
    var desc = document.head.querySelector('meta[name=description]');
    return desc ? desc.content : undefined;
}

I personally prefer to just get them in one object hash, then I can access them anywhere. This could easily be set to an injectable variable and then everything could have it and it only grabbed once.

By wrapping the function this can also be done as a one liner.

var meta = (function () {
    var m = document.querySelectorAll("meta"), r = {};
    for (var i = 0; i < m.length; i += 1) {
        r[m[i].getAttribute("name")] = m[i].getAttribute("content")
    }
    return r;
})();

My variant of the function:

const getMetaValue = (name) => {
  const element = document.querySelector(`meta[name="${name}"]`)
  return element?.getAttribute('content')
}

If you use JQuery, you can use:

$("meta[property='video']").attr('content');