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jQuery - How do I use AND with Selector?

My code's function is to alert user if the ptype textfield is empty.
$("input[name*='ptype']").each(function() {
if ($(this).val() == "") {
$(this).css({'background-color' : '#feffe3'});
e.preventDefault();
alert("Enter Value!");
}
});
However, I need to add another criteria where another field amount is not 0. So that the function get triggered when ptype="" && amount!=0. I'm very new in jQuery, and I'm not sure how to use AND operator in here. I've tried to do some based on other questions but it seems not working.
$("input[name*='ptype'][amount!='0']").each(function() {
$("input[name*='ptype'] , [amount!='0']").each(function() {
What am I missing ?

You can do it with && sign. Code depends on where your amount field is located and what it is. If I guess right it should be something like this:
$("input[name*='ptype']").each(function() {
if ($(this).val() == "" && $(this).parent().find(input[name='amount']).val() != 0) {
$(this).css({'background-color' : '#feffe3'});
e.preventDefault();
alert("Enter Value!");
}
});

That code $("input[name*='ptype'][amount!='0']").each(function() { is valid. You have to check the CSS selectors list.
The problem maybe in your *= selection. input[name*="ptype"] means Selects every element whose name attribute value contains the substring "ptype".
$('input[name*="ptype"][amount!="0"]').each(function() {
if ($(this).val() == "") {
$(this).css({'background-color' : '#feffe3'});
e.preventDefault();
alert("Enter Value!");
}
});
Take a look at this test https://jsfiddle.net/xpvt214o/211871/

« where another field» is the key in question.
So you need a selector to check if a selected element is empty and another element is not zero.
Holà!
Logic problem here.
with $(selector) you can look up for some elements.
There is no AND / OR in selectors for many sets of matching element.
A selector is ONE set of matching elements.
No way this selector can check for an attribute value of another set.
So you have to know your markup and navigate a bit... And take care of variable types.
$("input[name*='ptype']").each(function() {
if ( parseInt( $(this).next("input").val() ) != 0) {
$(this).css({"background-color" : "red"});
alert("Enter Value!");
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
ptype: <input type="text" name="ptype"><br>
amount: <input type="text" name="amount" value="1">
You have to look for another element's value here, from my understanding. So you have to know what is that "other" element and the methods to use may vary a lot depending on your HTML...

You can use this function in your button.
function check(e){
var verror = false;
$("input[name*='ptype']").each(function(index, value) {
var amount = $($("input[name='amount[]']").get(index)).val();
var ptype = $(this).val();
if(ptype.length <= 0 && amount.length > 0 ){
verror = true;
$(this).focus();
return false;
}
});
if(verror){
e.preventDefault();
alert("Enter Value!");
}
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form>
ptype: <input type="text" name="ptype[]">
amount: <input type="text" name="amount[]" value="1"> <br>
ptype: <input type="text" name="ptype[]">
amount: <input type="text" name="amount[]" value="2"> <br>
<button type="button" onclick="check(event)">Click</button>
</form>

JavaScript - Looping through elements and checking for length

I have some code that goes through the elements that end in '_ro' as below:
document.querySelectorAll("[id$=_ro]").forEach(function(element) {
element.readOnly = true;
});
Is there a way I can check to see if there is an input, and if there is a value input, set it to read only?

Try element.nodeName == 'INPUT' to check the node name and element.value.length to check the value length:
document.querySelectorAll("[id$=_ro]").forEach(function(element) {
if(element.nodeName == 'INPUT' && element.value.length)
element.readOnly = true;
});
<input id="name_ro" type="text" value="Jhon"/>
<div id="div_ro">test</div>
<input id="phone_ro" type="text"/>

Input box validation when there is no input

I am trying to make a simple calculator. You enter one number, you enter the second one, press PLUS and get alert with an answer. I need to show alert('no data') if you click on PLUS when input fields are not touched.
function num1() {
nm = document.getElementById('nsum1').value;
}
function num2() {
mn = document.getElementById('nsum2').value;
}
function plus() {
sum = +nm + +mn;
if (nm == null || mn == null) {
alert('no data');
} else {
alert(sum);
}
}
<input onchange="num1()" id="nsum1" name="numb" type="tel" placeholder="number" maxlength="6" />
<span onclick="plus()" id="sum">PLUS</span>
<input onchange="num2()" id="nsum2" name="numb" type="tel" placeholder="number" maxlength="6" />
So far I have tried if(sum == undefined)/if(sum == null)/if(sum == false)/if(isNaN(sum))/if(sum == "") and nothing seems to work.

If you haven't touched the input field and get the value, then the result would be ""
You need a condition like
if (nm == "" || mn == "") {
alert('no data');
}
And also you should do operation after validations. You are doing operation and then validating.
Fixed other issues aswell.
function plus() {
mn = document.getElementById('nsum2').value;
nm = document.getElementById('nsum1').value;
if (nm == "" || mn == "") {
alert('no data');
} else {
sum = +nm + +mn;
alert(sum);
}
}
<input id="nsum1" name="numb" type="tel" placeholder="number" maxlength="6" />
<span onclick="plus()" id="sum">PLUS</span>
<input id="nsum2" name="numb" type="tel" placeholder="number" maxlength="6" />

You can do it much easier
function plus(num1, num2) {
alert(isNaN(num1) || isNaN(num2) ? 'No data' : num1 + num2);
}
function getNumber(id) {
return parseFloat(document.getElementById(id).value);
}
<input id="nsum1" type="number" placeholder="number" maxlength="6" />
<span onclick="plus(getNumber('nsum1'), getNumber('nsum2'))" id="sum">PLUS</span>
<input id="nsum2" type="number" placeholder="number" maxlength="6" />

I've made some changes to your code to make it more robust. See the inline comments for a description.
Declare variables
It is important to declare your variables, when you don't all the variables you are using will wind up in the global scope. When you Google this you will find many articles like this one: https://gist.github.com/hallettj/64478.
Prevent polluting the global scope. In a small website this may not be much of an issue but when working on larger project or with third party code, this is a must. The link above also explains this to some extend.
Use a button If you want something to be interactive, use an HTML element that was meant for it. The button element should be used, it has all sorts of accessibility features the span doesn't have. For instance, by default it will receive focus when navigating your website with the tab key.
Use descriptive variable names nm and mn may mean something to you now but in 6 months it will be a complete mystery. It also makes the code more readable and thus easier to maintain.
Attach event listeners in JS In general it is a bad idea to assign event listeners through the HTML attribute onXXX="". It is more error prone and a lot more time intensive when you want to change something.
// Wrap your code in a closure to prevent poluting the global scope.
(function() {
// Always declare your variables. These variables are no longer scoped to the window object but are no scoped to the function we're in.
var
valueA = null,
valueB = null;
/**
* To check if your input is a valid number requires a couple of checks.
* It is best to place these into their own method so you're other
* method is more readable.
*/
function isNumber(value) {
if (
// == null checks for undefined and null
value == null ||
value === '' ||
isNaN(value)
) {
return false;
}
return true;
}
function onChangeHandler(event) {
var
// Get the element that dispatched the event.
target = event.target;
// Check if the target has the class we've assigned to the inputs, of not you can ignore the event.
if (!target.classList.contains('js-input')) {
return;
}
// Based on the ID of the target, assign the value to one of the variables for the values.
switch(target.id) {
case 'nsum1':
valueA = parseFloat(target.value);
break;
case 'nsum2':
valueB = parseFloat(target.value);
break;
}
}
function onSumTriggerClicked(event) {
// Check if there are numbers to work with
if (
!isNumber(valueA) ||
!isNumber(valueB)
) {
// If not alert the user
alert('no data');
return;
}
sum = valueA + valueB;
alert(sum);
}
function init() {
var
// Get the calculator element.
calculator = document.getElementById('calculator'),
// Get the button to sum up the value.
sumButton = document.getElementById('sum-trigger');
// Add an event listener for the change event.
calculator.addEventListener('change', onChangeHandler);
// Add an event listener for the click event.
sumButton.addEventListener('click', onSumTriggerClicked);
}
// Call the init method.
init();
})();
<div id="calculator">
<input class="js-input" id="nsum1" name="numb" type="tel" placeholder="number" maxlength="6" />
<button type="button" id="sum-trigger" id="sum">PLUS</button>
<input class="js-input" id="nsum2" name="numb" type="tel" placeholder="number" maxlength="6" />
</div>

Try to track it via Inspector, maybe log the values of nm and mn before anything else and correct your condition accordingly(as the sample).
function plus() {
console.log(nm);
sum = +nm + +mn;
if (nm == null || mn == null) {
alert('no data');
}
It will most likely just be blank. So in this case you can modify your condition into:
if (nm === '' || mn === '') {...}
Hope it will help

Please use this as reference.
I've fixed your code.
if ( num1 === '' && num2 === '' ) {
alert('no data');
} else {
alert( parseInt(num1) + parseInt(num2) );
}

Getting function to run as user types

I have a phone number input that I am trying to get the dashes to appear in the number as the user types.
I am wanting the number to appear as 555-555-5555.
The function works for the most part, but the dashes aren't entered until after the whole number is entered. I am using the keyup function, which I thought would solve this, but no luck.
Does anyone have any recommendations as to what I have to do to get the dashes to be entered as the user types in the digits?
$('#phone').keyup(function() {
$(this).val($(this).val().replace(/(\d{3})\-?(\d{3})\-?(\d{4})/,'$1-$2-$3'))
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div>
<label class="contact-label">Phone Number:</label>
<input type="tel" class="contact_input" name="phone" id="phone">
</div>

I modified your code slightly to produce something that I think is a little easier to read, but still does the job.
I just evaluated the length of the <input /> tag's value on each .keyup() event and then augmented the value accordingly. Take a look at the snippet below:
--UPDATE--
After comments regarding backspacing issues I added a couple lines of code that seem to fix the issue:
First I checked for either backspace or delete .keyup() events to prevent the formatting code from interfering with correcting errors in the number.
I also added a few checks, and a global formatFlag variable to ensure that if the user backspaces to an awkward index like 3 or 6(where hyphens would normally be added), that formatting would resume as normal on the next .keyup() event.
let formatFlag = false;
$(function(){
$('#phone').keyup(function(evt) {
let modifiedValue = $(this).val().replace(/-/g, "");
if(evt.keyCode == 8 || evt.keyCode == 46) { //8 == backspace; 46 == delete
//Checks whether the user backspaced to a hyphen index
if(modifiedValue.length === 3 || modifiedValue.length === 6) {
//Checks whether there is already a hyphen
if($(this).val().charAt($(this).val().length - 1) !== '-') {
formatFlag = true; //Sets the format flag so that hyphen is appended on next keyup()
} else {
return false; //Hyphen already present, no formatting necessary
}
} else {
formatFlag = false;
}
return false; //Return if backspace or delete is pressed to avoid awkward formatting
}
if(!!formatFlag) {
// This re-formats the number after the formatFlag has been set,
// appending a hyphen to the second last position in the string
$(this).val($(this).val().slice(0, $(this).val().length - 1) + '-' +
$(this).val().slice($(this).val().length - 1));
formatFlag = false; //Reset the formatFlag
}
if(modifiedValue.length % 3 == 0) {
if(modifiedValue.length === 0 || modifiedValue.length >= 9){
return false;
} else {
$(this).val($(this).val() + '-');
return;
}
}
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div>
<label class="contact-label">Phone Number:</label>
<input type="tel" class="contact_input" name="phone" id="phone" />
</div>

Javascript prevent empty space before character

HTML:
<input id=MyTextBox type="text" onkeypress="MyFunction()" />
<input id=MyButton type="button" onclick="Control()" />
Onkeypress Javascript :
I want to do below example , however i have not integrated according to "MyTextBox"
http://jsfiddle.net/2cYeu/9/
There must not be no space before character in textbox.

TRY this DEMO
For the first time space is not allowed later its allowed
function call(e) {
if (document.getElementById('nospace').value.length == 0) {
if (e.keyCode == 32) {
e.preventDefault();
}
}
}

function Control() {
var text = document.getElementById("MyTextBox").value;
if (text.charAt(0)==" ") {
alert("First Chart is space");
}
}
This works I have tested it
Also, to the left of jsfiddle, don't select "onDOMReady"
select no wrap in body
That's the problem why you get those errors