Scale down a small JS Code section of the image proportionally _ Javascript tutorial

Javascript: A small JS Code section of the scaled down image. Javascript tutorial I wrote a very simple image thumbnail JS Code. Of course there are a lot of similar code on the Internet, which is really ugly here.
The main method is to write SetImgSize. js in SetImgSize. js.
1 // smart thumbnail image JS method
2 // parameter: imgID (ID of the image)
3 // parameter: maxWidth (the maximum width of the image. If the value is 0, the width is not limited)
4 // parameter: maxHeight (the maximum Image Height. If the value is 0, the image height is not limited)
5 function setImgSize (imgID, maxWidth, maxHeight)
6 {
7 var img = document. images [imgID];
8 if (maxWidth <1)
9 {
10 if (img. height> maxHeight)
11 {
12 img. height = maxHeight;
13}
14 return true;
15}
16 if (maxHeight <1)
17 {
18 if (img. width> maxWidth)
19 {
20 img. width = maxWidth;
21}
22 return true;
23}
24 if (img. height> maxHeight | img. width> maxWidth)
25 {
26 if (img. height/maxHeight)> (img. width/maxWidth ))
27 {
28 img. height = maxHeight;
29}
30 else
31 {
32 img. width = maxWidth;
33}
34 return true;
35}
36} function implementation principle is to use JS to implement micro-contraction after the image is loaded (onload event.
The following is a test file test.htm.
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2
3
4Test
5