why can't i change the width of the rect in svg? html and javascript

Question

why can't i change the width of the rect in svg? i wrote these lines of code:
in js file:
window.onload=function() {
var bone = document. getElementById("building");
bone. width="50";
} ;
in html:
i defined the script of java
<rect id="building" width="100" height="150" x="0" y="150" />

the html code works it just doesn't change the width..

Answer 1

how can i use the dom with the svg, what should i do?!

Answer 2

dom doesn't have width property