I would like to know how I can validate the input value that comes from a Datalist
. I mean, if I have a Datalist
where the user can start to write
I'd like to share a non-jquery alternative, only in Js:
function is_valid_datalist_value(idDataList, inputValue) {
var option = document.querySelector("#" + idDataList + " option[value='" + inputValue + "']");
if (option != null) {
return option.value.length > 0;
}
return false;
}
function doValidate() {
if (is_valid_datalist_value('colours', document.getElementById('color').value)) {
alert("Valid");
} else {
alert("Invalid");
}
}
<form onsubmit="return false">
<input type="text" id="color" list="colours">
<datalist id="colours">
<option value="Red" data-id="1" />
<option value="Blue" data-id="2" />
<option value="Green" data-id="3" />
<option value="Black" data-id="4" />
<option value="White" data-id="5" />
</datalist>
<button onclick="doValidate();">Send</button>
</form>
If you use jQuery
find method, it will traverse the DOM
tree trying to find the correct element taking into account the value of one of its attributes, and looking at your comment, I think that you are concerned about performance.
Your first idea about iterate over all the options and check the value property is better (speaking about performance) than traversing the DOM
tree looking for an element with a particular value in one of their attributes (look at this comparison). You need to be aware that shorter code is not the same as faster code.
A faster solution is to generate an array
of strings at the beginning and search the correct value inside it in the validation process:
//---At the beginning of your application
let list = Array.prototype.map.call(document.getElementById("colours").options, (option) => option.value);
//---Later in your validation process
if (list.indexOf(value) < 0) {
//Invalid
}
Another faster solution is to generate an object
at the beginning and use it as a hash map, checking for the correct value inside it in the validation process:
//---At the beginning of your application
let hashmap = Array.prototype.reduce.call(document.getElementById("colours").options, (obj, option) => {
if (!obj[option.value]) { obj[option.value] = true; }
return obj;
}, {});
//---Later in your validation process
if (!hashmap[value]) {
//Invalid
}
Here you have the four methods compared in measurethat:
1 - Your first idea (iterate over all the Datalist
options)
2 - Use the jQuery
find method (@nsthethunderbolt solution)
3 - Create an array
of strings
at the beginning and search the value in the Array
in the validation process
4 - Create a hash map at the beginning and check if the value is true
in the validation process
https://www.measurethat.net/Benchmarks/Show/4430/0/search-an-option-inside-a-datalist
Try this:
<input type="text" list="colours" id='txt'>
And on form submit you can check:
var val = $("#txt").val();
var obj = $("#colours").find("option[value='" + val + "']");
if(obj != null && obj.length > 0)
alert("valid"); // allow form submission
else
alert("invalid"); // don't allow form submission
You can do this with HTML5 validation using pattern
. It's easier if you're populating your datalist with some sort of template, but it would look something like this (Note that you would need additional code to handle the validation - I just added very simple CSS to display the validation state)
input:valid {
border: 1px solid green;
}
input:invalid {
border: 1px solid red;
}
<input type="text" list="colours"
pattern="^(Red|Blue|Green|Black|White)$"
>
<datalist id="colours">
<option value="Red" data-id="1">
<option value="Blue" data-id="2">
<option value="Green" data-id="3">
<option value="Black" data-id="4">
<option value="White" data-id="5">
</datalist>