When I execute the eval function it doesn't turn my json response into a object it just breaks my code. I've tried parsing with prototype.js and JSON2.js to no avail some please explain what I am doing wrong here?
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Inventory Management</t开发者_如何转开发itle>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Untitled Document</title>
<script src="call.js" type="text/javascript"></script>
<script src="prototype.js" type="text/javascript"></script>
</head>
<body>
<div>
<p id="resp" >new</p>
<script type="text/javascript">
var xhr;
var results=getPlants(xhr,results);
var plants;
function getPlants(xhr,results){
try {
xhr=new XMLHttpRequest();
}catch(microsoft){
try{
xhr=new ActiveXObject("Msxml2.XMLHTTP");
}catch(othermicrosoft){
try{
xhr = new ActiveXObject("Microsoft.XMLHTTP");
}catch(failed){
xhr=false;
alert("ajax not supported");
}
}
}
xhr.onreadystatechange= function () {
if(xhr.readyState==4 && xhr.status==200) {
results = xhr.responseText;
}
}
xhr.open("GET","db_interactions.php",true);
xhr.send(null);
alert("sent");
return results;
}
plants = eval('('+results+')');
document.write(typeof(plants));
</script>
</div>
</body>
</html>
You're issuing an asynchronous request. That means the function will return even when the data isn't ready yet. But your call assumes the JSON response is ready when getPlants is called. Which obviously makes results undefined because you aren't waiting for it.
Put your
plants = eval('('+results+')');
document.write(typeof(plants));
Inside the xhr.onreadystatechange function to make it work, or open the connection as synchronous
xhr.open("GET","db_interactions.php",false);
By the way, don't use eval to parse JSON because code may be injected maliciously. Use a JSON parser instead.
![Interactive visualization of a graph in python [closed]](https://www.devze.com/res/2023/04-10/09/92d32fe8c0d22fb96bd6f6e8b7d1f457.gif)
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