Here's a simple example you can expand on:
<html><head>
<meta content="text/html; charset=ISO-8859-1" http-equiv="content-type">
<title>Test Page</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script>
function postIt(){
var valueToPost = $('#field1').val();
var formData = {api_key:"YOURAPIKEYHERE",field1:valueToPost};
$.ajax({url : "https://api.thingspeak.com/update",
type: "POST",
data : formData,
success: function(data, textStatus, jqXHR){ if (data==="0") {alert("Channel not updated");} else {alert("New entry " + data + " added to channel");}},
error: function (jqXHR, textStatus, errorThrown) { alert("Error posting data");}
});
};
</script>
<meta content="text/html; charset=ISO-8859-1" http-equiv="content-type">
<title>Test Page</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script>
function postIt(){
var valueToPost = $('#field1').val();
var formData = {api_key:"YOURAPIKEYHERE",field1:valueToPost};
$.ajax({url : "https://api.thingspeak.com/update",
type: "POST",
data : formData,
success: function(data, textStatus, jqXHR){ if (data==="0") {alert("Channel not updated");} else {alert("New entry " + data + " added to channel");}},
error: function (jqXHR, textStatus, errorThrown) { alert("Error posting data");}
});
};
</script>
</head>
<body>
<h1>Example HTML page
<form action="" method="get">
<p>
<label>Desired Temperature: </label>
<input id ="field1" type="text" value=""><br><br>
<input value="Update ThingSpeak" type="button" onClick=postIt()>
</p>
</form>
</h1>
</body>
</html>
You can remove the alert()'s if you don't want the page to display alerts. If this is confusing you may want to take some basic javascript classes.