Javascript verifies whether the URL address entered by the user is empty and the format is correct_javascript skills

Copy code The code is as follows:

<script type="text/javascript">
function checkUrl() {
var url = document.getElementById('url').value;
if (url==''){
alert('URL address cannot be empty');
return false;
} else if (!isURL(url)) {
alert('The format of URL should be http://www.jb51.net');
return false;
} else {
return true;
}
return false;
}

function isURL(str)
{
//varreg=/[0-9a-zA-z] .(html|htm|shtml|jsp|asp|php|com|cn|net|com.cn|org)$/;
//Must contain . (the last . is preceded by at least one character) and . is followed by at least one word character. The last character must be a word character or /
varreg=/w .(w |w /)$/;
varisurl=reg.test(str);//The test(str) method is a built-in object of js correct expression and can be called directly
returnisurl;
}
</script>

Copy code The code is as follows:

<form action="" method="post" onsubmit="checkUrl();">

URL:
<input type="text" name="url" id="url" value="http://www.jb51.net" onfocus="this.value=''"/>
<br /><br />
<input type="submit" value="Get address" name="get"/>
<input type="submit" value="Download" name="download"/>
</form>

PHP detects URL address validity

The code is as follows

Copy code The code is as follows:

<?
function is_url($str){
return preg_match("/^http://[A-Za-z0-9] .[A-Za-z0-9] [/=?%-&_~`@[]': !]*([^< ;>"])*$/", $str);
}
?>

If you want to try if it works normally, we can use the file_get_contents() function to verify it.