Is it possible to directly use the result of a Javascript function as an input value for an HTML form?
<form class="my-form" action="fileUpload.php" method="POST" enctype="multipart/form-data">
<input type="hidden" name="User_id" value="getValue();">
<input type="submit" value="Submit"/>
</form>
This is clearly not correct, but I hope it communicates what I am trying to do. I would like the returned result of JS function getValue(); to act as the input value.
In that implementation, no it is not possible to equate the value attribute inside the input tag to a JavaScript function.
According to w3.org, the value attribute can only equal
String without line breaks
Any string that contains no line feed (U+000A, “LF”) or carriage return (U+000D, “CR”) characters.
I am not sure what is inside the getValue() function, but you can call a click event handler when the submit button is clicked and run that getValue() function.
Ex.
<form class="my-form" action="fileUpload.php" method="POST" enctype="multipart/form-data">
<input type="hidden" name="User_id">
<input type="submit" value="Submit" onclick="getValue();"/>
</form>
I hope it guides you well.
input[name='User_id'] to 'getValue();'While it is technically possible to do something like this:
<script>
function getValue(){ return "foo"; }
document.write("<input type='hidden' name='User_id' value='" + getValue() + "' />");
</script>
That is typically frowned upon as there are scoping issues and page rendering implications. The more accepted way would be to do something more like this..
function getValue(){ return "bar"; }
window.addEventListener("load", function(event){
document.querySelector("input[name='User_id']").value = getValue();
});
or potentially at form submit or submit button click with something like:
function getValue(){ return "bar"; }
document.querySelector("input[type='submit']").addEventListener("click", function(){
document.querySelector("input[name='User_id']").value = getValue();
});
Though I am not keen on it myself, it would be possible to do the same as above with:
<input type="submit" value="Submit" onclick="setUserId();"/>
Then later in say a end of body script block do:
function getValue(){ return "bar"; }
function setUserId(){
document.querySelector("input[name='User_id']").value = getValue();
}
