Why can't I use local variable in a function?

Question

I have a question about setTimeout, my code follows:

<script type="text/javascript">
    var s =-1;
    setImage();
    function setImage(){
        var img=new Array();
        var url=new Array();
        img[0]="images/oak.gif";url[0]="http://oakland.athletics.mlb.com/";
        img[1]="images/was.gif";url[1]="http://washington.nationals.mlb.com/";
        img[2]="images/chc.gif";url[2]="http://chicago.cubs.mlb.com/";
        img[3]="images/sd.gif";url[3]="http://sandiego.padres.mlb.com/";
        s+=1;
        if(s>=img.length){
            s==0;
        };
        document.getElementById("imgsrc").src=img[s];
        document.getElementById("imghref").href=url[s];
        setTimeout(setImage,1000);
    };
</script>

And I'm confused as to why I can't change var s=-1 in the function setImage(), like:

        **var s=-1**
        s+=1;
        if(s>=img.length){
            s==0;
        };

The function doesn't work. I thought the problem is about global and local variable, but I don't have a clear view.

the code result will be

		var s =-1;
		setImage();
		function setImage(){
			var img=new Array();
			var url=new Array();
			img[0]="https://imgur.com/sfAyT6s.gif";url[0]="http://oakland.athletics.mlb.com/";
			img[1]="https://imgur.com/av5hb4a.gif";url[1]="http://washington.nationals.mlb.com/";
			img[2]="https://i.imgur.com/zGKLMPh.gif";url[2]="http://chicago.cubs.mlb.com/";
			img[3]="https://i.imgur.com/ZBXTL5s.gif";url[3]="http://sandiego.padres.mlb.com/";
			s+=1;
			if(s>=img.length){

				s=0;
			};
			document.getElementById("imgsrc").src=img[s];
			document.getElementById("imghref").href=url[s];
			setTimeout(setImage,1000);
		};

	...
	<div>	
		<a id="imghref" href="http://chicago.cubs.mlb.com/">
			<img id="imgsrc" src="images/chc.gif">
		</a>
	</div>
	...

For completeness, please add the result you're getting right now. You might also want to add console logging (at least for the values of s and img.length) and share the results of that. That will help you as well as the forum members to troubleshoot the code. Are any images displaying? Is the setTimeout called as expected? — Michal
– Michal, Commented Aug 26, 2018 at 3:48

Phil · Accepted Answer · 2018-08-26 03:42:16Z

1

In your if statement, you wrote s==0. The == operator is a comparison operator. It's asking "is s equal to 0?" If your intention was to set s to zero, then write s=0 instead.

answered Aug 26, 2018 at 3:42

Phil

1361 silver badge10 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Why can't I use local variable in a function?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related