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I have the following simple code from an exercise in Modern Javascript used to calculate a sphere's volume, it contains a part which checks to make sure that a value has been entered for radius.
I put in a negative number to test the function, and it works, but I was interested in what would be displayed in the console, so I checked. I end up seeing an error flash in the log and then disappear - too quick to read.
Is this just what occurs when an if statement evaluates to false? Why is this error displaying and then being cleared almost immediately? I'm aware I could use another way to debug this (a.k.a. using console.log or logging the problem by some other means), I'm just interested as to why this error disappears.
HTML:
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Volume of a Sphere Calculator</title>
<!--[if lt IE 9]>
<script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script>
<![endif]-->
<link rel="stylesheet" href="css/styles.css">
</head>
<body>
<!-- sphere.html -->
<form action="" method="post" id="theForm">
<fieldset>
<p>Use this form to calculate the volume of a sphere.</p>
<div>
<label for="radius">Radius</label>
<input type="text" name="radius" id="radius" required></div>
<div>
<label for="volume">Volume</label>
<input type="text" name="volume" id="volume"></div>
<div>
<input type="submit" value="Calculate" id="submit"></div>
</fieldset>
</form>
<script src="js/sphere.js"></script>
</body>
</html>
JS:
function calculate() {
'use strict';
var volume;
var radius = document.getElementById('radius');
if (radius && (radius.value > 0)){
volume = (4/3) * Math.PI * Math.pow(radius.value, 3);
}
volume = volume.toFixed(4);
document.getElementById('volume').value = volume;
return false;
}
function init() {
'use strict';
var theForm = document.getElementById('theForm');
theForm.onsubmit = calculate;
}
window.onload = init;
903
Because this is the top Google match for my problem of console.log output appearing and quickly disappearing, this happened to me because I either had an empty set of label tags out of place or a form with no action. Deleting those tags caused JavaScript and console.log() to work like it was supposed to.
75
Adding another solution as a Google search for "javascript log disappearing" brought me here.
Page refreshing/navigation was the problem.
Selecting "Preserve log" in the console settings as per mateuszb's comment solved the issue.
29
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