Why do I get Uncaught SyntaxError: Unexpected identifier if it works once?

There are a bunch of these on StackOverflow. The punchline is usually a typo somewhere in the script.

It works once, then it gives 1 error message a second.

Here I am changing the colors of states on a map:

<!-- language: lang-js -->
<script type="text/javascript">
colors = [ 'rgba(255,0,0,0.1)','rgba(0,255,0,0.1)','rgba(0,0,255,0.1)'  ];

$(document).ready(function(){

    setInterval(
        $("ul").children().eq( Math.floor(50*Math.random())).css('color', colors[Math.floor(3*Math.random())] )
    ,1000);

});
</script>

Why do I get Uncaught SyntaxError: Unexpected identifier if it works once?

There are a bunch of these on StackOverflow. The punchline is usually a typo somewhere in the script.

It works once, then it gives 1 error message a second.

Here I am changing the colors of states on a map:

<!-- language: lang-js -->
<script type="text/javascript">
colors = [ 'rgba(255,0,0,0.1)','rgba(0,255,0,0.1)','rgba(0,0,255,0.1)'  ];

$(document).ready(function(){

    setInterval(
        $("ul").children().eq( Math.floor(50*Math.random())).css('color', colors[Math.floor(3*Math.random())] )
    ,1000);

});
</script>

• javascript
• jquery

2 Answers 2

You are missing function(){} to wrap your code.

setInterval(function(){
    $("ul").children().eq( Math.floor(50*Math.random())).css('color', colors[Math.floor(3*Math.random())] )
},1000);

it works once because it executes your inner-code looking for a function or string to be returned. When one isn't, it fails with a js error.

setInterval accept parametres in quotes:

<script type="text/javascript">
colors = [ 'rgba(255,0,0,0.1)','rgba(0,255,0,0.1)','rgba(0,0,255,0.1)'  ];

$(document).ready(function(){

    setInterval(
        '$("ul").children().eq( Math.floor(50*Math.random())).css("color", colors[Math.floor(3*Math.random())] )'
    ,1000);

});
</script>