更改属性Javascript方式的值

Question

I have a problem here, or more like confused. So I know the basics of changing attribute in html via javascript. For example:

<iframe id="iframe" src="http://www.stackoverflow.com/" width="610px">

So to change the attribute of width for element with id "iframe" would be:

document.getElementById("iframe").setAttribute("width", "700px");

But how can I change attribute via javascript when it comes like this way? (notice the difference between width's attribute)

<iframe id="iframe" src="http://www.stackoverflow.com/" width=610>

Answer 1

But how can I change attribute via javascript when it comes like this way?

Exactly the same:

.setAttribute("width", "700px");

or

.setAttribute("width", "700");

or

.setAttribute("width", 700);

Note that all attribute values are considered to be strings anyways. The HTML syntax just allows you to omit quotation marks in certain circumstances, but that doesn't change the datatype. From the HTML specification :

By default, SGML requires that all attribute values be delimited using either double quotation marks (ASCII decimal 34) or single quotation marks (ASCII decimal 39).

[...]

In certain cases, authors may specify the value of an attribute without any quotation marks. The attribute value may only contain letters (az and AZ), digits (0-9), hyphens (ASCII decimal 45), periods (ASCII decimal 46), underscores (ASCII decimal 95), and colons (ASCII decimal 58). We recommend using quotation marks even when it is possible to eliminate them.

If you look at the DOM API specification , you can see that setAttribute is defined to accept a DOMString as argument. The JavaScript implementation will convert any value you pass to this method accordingly.

Answer 2

Exactly the same way. Although, in your second example, you didn't set the the id properly.

<iframe id="iframe" src="http://www.stackoverflow.com/" width=610>
<--       ^ added equal sign here                              -->

With that change your code works fine: http://jsfiddle.net/FECq3/