How to make javascript continue even if element is not present - javascript

Here's my problem: the following code stops working if elements above #sizem and/or #sizedivided is not present. The ecommerce store removes the elements/id when a product doesn't require said elements/id.
It seems to me that the code only works if all elements are present at the same time.
Is there another way to do this and avoid the code stopping?
This is supposed to be aplied to a a dropdown with an alert if the user hasn't selected a size and/or color when attempting to purchase/add to basket
$('#prod-buy').click(function(){
if ($("#color")[0].selectedIndex <= 0) {
alert("Select color");
return false;
}
if ($("#sizem")[0].selectedIndex <= 0) {
alert("Select size");
return false;
}
if ($("#sizedivided")[0].selectedIndex <= 0) {
alert("Select size");
return false;
}
});

You should be checking whether each element is present.
With jQuery use the length property:
if($('#sizem').length) {
if ($("#sizem")[0].selectedIndex <= 0) {
alert("Select size");
return false;
}
}

you need to test on whether there's an element. Straight from your code you could do this
$('#prod-buy').click(function(){
if ($("#color")[0] && $("#color")[0].selectedIndex <= 0) {
alert("Select color");
return false;
}
if ($("#sizem")[0] && $("#sizem")[0].selectedIndex <= 0) {
alert("Select size");
return false;
}
if ($("#sizedivided")[0] && $("#sizedivided")[0].selectedIndex <= 0) {
alert("Select size");
return false;
}
});
that way you test wether there's an object before trying to access a property of it (or of undefined). There are other ways to clean it up, but requires more restructuring your code and would thus hide the cuase for you

Related

Is it possible to call a method from a class in an HTML event like 'onblur'?

I got a little problem that I can't solve...
I usually check my form like this:
function checkFirst(field) {
if (field.value.length < 2 || !regLetters.test(field.value)) {
//do something
} else {
//do something else
firstNameOk = true;
}
}
and on the HTML side with onblur="checkFirst(this)".
Now I'm using OOP and I can't use my methods in onblur and I don't know how I could call the class in the onblur HTML attribute...
I already got a solution to work around this without using onblur in HTML and in my case I'd like to know if it's possible or not.
Anyone to help me please?
Edit:to avoid people telling me to use addEventlistener i show you my solution that works fine but not the one i wanted to use...
this.data.forEach(item => item.addEventListener('blur', function () {
console.log(item.id)
// check first name field //
if (item.id === "first") {
if (item.value.length < 2 || !this.regLetters.test(item.value)) { // if this field length =
this.highlightField(item, true);
} else {
this.highlightField(item, false);
this.errorMessagesReset(item);
this.firstNameOk = true;
}
// check last name field //
} else if (item.id === "last") {
if (item.value.length < 2 || !this.regLetters.test(item.value)) {
this.highlightField(item, true);
} else {
this.highlightField(item, false);
this.errorMessagesReset(item);
this.lastNameOk = true;
}
// check email field //
} else if (item.id === "email") {
if (item.value.length < 2 || !this.regmail.test(item.value)) {
this.highlightField(item, true);
} else {
this.highlightField(item, false);
this.errorMessagesReset(item);
this.emailOk = true;
}
// check textarea field //
} else if (item.id === "message") {
if (item.value.length < 1 || item.value > 100) { // if length of item is sup or equal to 1 and
this.highlightField(item, true);
} else {
this.highlightField(item, false);
this.errorMessagesReset(item);
this.messageOk = true;
}
}
}.bind(this))); ```
It should be a static function that belongs to the class then. That way you can call it directly.

Why doesn't the removeChild remove the element?

I have written this scrip to take out ads on a website. Was working on it the whole day.
This is the JS code:
var timer = setInterval(deletor, 1);
function deletor() {
timer;
var slider = document.querySelector("#slider-con");
var bannerTop = document.querySelector("#MainContent > div:nth-child(2)")
var bannerMiddle = document.querySelector("#MainContent > iframe");
var bannerRandom = document.querySelector("#MainContent > div:nth-child(7)");
var bannerRandom2 = document.querySelector("#MainContent > div:nth-child(6)");
if (slider == undefined) {
return false;
} else {
slider.parentNode.removeChild(slider);
};
if (bannerTop == undefined) {
return false;
} else {
bannerTop.parentNode.removeChild(bannerTop);
};
if (bannerMiddle == undefined) {
return false;
} else {
bannerMiddle.parentNode.removeChild(bannerMiddle);
};
if (bannerRandom == undefined) {
return false;
} else {
bannerRandom.parentNode.removeChild(bannerRandom);
};
if (bannerRandom2 == undefined) {
return false;
} else {
bannerRandom2.parentNode.removeChild(bannerRandom2);
};
};
Now, as you can see, it gets the values first and then goes through if statements. Idea behind this is: On first try, it deletes the elements and on the second one, it stops the function.
But when I inserted this last element, it won't delete it. The ID is correct, everything is correct but it won't delete the element, so I keep getting the same alert over and over.
Also, I found out that, I get this banner ad on two places. When I have "var bannerRandom = document.querySelector("#MainContent > div:nth-child(7)");" this, it appears as "document.querySelector("#MainContent > div:nth-child(6)")" this, and when I have both, it appears as "document.querySelector("#MainContent > div:nth-child(6)")" this. And it's not deleted.
Console shows no errors.
Your various statements in the form:
if (slider == undefined) {
return false;
} else {
slider.parentNode.removeChild(slider);
};
mean this: "If slider wasn't found in the DOM, exit the function. Otherwise, remove the slider and continue the function."
So that means your function will terminate the first time one of the elements you're looking for doesn't exist. Since it terminates then, none of the other elements after it is checked. That seems unlikely to be what you want to do.
You probably just wanted:
if (slider) {
slider.parentNode.removeChild(slider);
}
...and so on.
Note that you don't put ; at the end of a block attached to a flow-control statement like if or else, which is why I've removed it above. (Doing so is harmless, because JavaScript ignores them; but it's pointless.)

How to refactor long if statment?

I have a long if statement that I'm wanting to refactor. The statement listens for a click and then updates one of five text boxes depending on if those text boxes have anything in them or not. How could I change my code to be more efficient.
$('#img1').click(function() {
if ($('#card1').val().length === 0) {
$('#card1').val('A feeling of warmth');
} else if ($('#card2').val().length === 0) {
$('#card2').val('A feeling of warmth');
} else if ($('#card3').val().length === 0){
$('#card3').val('A feeling of warmth');
} else if ($('#card4').val().length === 0){
$('#card4').val('A feeling of warmth');
} else if ($('#card5').val().length === 0){
$('#card5').val('A feeling of warmth');
}
});
you could use a loop
$('#img1').click(function() {
var items = ["#card1", "#card2", "etc"];
for(var i=0;i<items.length;i++){
if ($(items[i]).val().length === 0) {
$(items[i]).val('A feeling of warmth');
}
}
});
it's at least easier to read. Also if your buttons are always card + a number you could make it even simplier (not easier to read, just less lines & maintenance)
$('#img1').click(function() {
for(var i=0;i<=5;i++){
if ($("#card" + i).val().length === 0) {
$("#card" + i).val('A feeling of warmth');
}
}
});
It seems like you're using JQuery. You can use a selector and a filter to isolate the first empty item:
$('#img1').click(function() {
$('input:text[id^=card]')
.filter(function() { return $(this).val() == ""; })
.first()
.val('A feeling of warmth');
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button id="img1">CLICK ME</button><br>
<input id="card1"><br>
<input id="card2"><br>
<input id="card3"><br>
<input id="card4"><br>
<input id="card5">
$('input:text[id^=card]') selects all text inputs whose IDs begin with 'card'. But the same principle would apply to other element types.
$('#img1').click(function() {
// num can be total count of the element like $(.card).children.count
var num = 5, // preferably dont make it hardcoded.
str = 'A feeling of warmth',
preIdStr = '#card',
id;
for (var i = 1; i <= num; i += 1) {
id = preIdStr + i;
if ($(id).val().length === 0) {
$(id).val(str);
}
}
});
Give all cards the same class.
Then use the selector $('.yourclass')
Now use the jQuery for-each (.each) function to iterate all elements. Within the loop you check the value, set it to whatever you want and return false when the value was set, since this exit's the loop.
$('.yourclass').each(
function () {
if (this.val().length === 0) {
this.val('your value');
return false; // exit loop
}
});

Validate multiple textboxes

I have this code that validates if ContentPlaceHolder1_locationTextBox has text in it before newIndex can become 3.
if ((newIndex === 3 && $("#ContentPlaceHolder1_locationTextBox").val() == "")) {
$('#ContentPlaceHolder1_locationLabelV').show();
return false;
}
else {
$('#ContentPlaceHolder1_locationLabelV').hide();
}
However I also have ContentPlaceHolder1_countryTextBox & ContentPlaceHolder1_seaTextBox on the page with thier respective labels, how can I modify the script so that it validates against all textboxes?
I tried adding a horrible or statement however this was causing the page to freeze. What s the best method to check against all three textboxes?
You can add class for all inputs, example: validate
After you can create JS function. You can fire this function as you wish.
function check(){
$('.validate').each(function(){
label = $("label[for='"+$(this).attr('id')+"']");
if ((newIndex === 3 && $(this).val() == "")) {
label.show();
return false;
}
else {
label.hide();
}
});
}
function validate(value) {
if ...
//show div
else ...
// hide div
}
$("input[type='text']").each(function(){
//value from input text field
var myval = $(this).val();
//call validation function
validate(myval);
});

How do I call this function on blur(), using JQuery?

I have this function, see below:
function checkStartPrice (){
if ($('#StartingPrice')[0].value.length == 0){
alert("The 'Starting Price' cannot be left empty!");
return false;
} else {
var BuyItNowPrice = parseFloat($('#BuyItNowPrice').val());
var StartingPrice = parseFloat($('#StartingPrice').val());
var Reserve = parseFloat($('#Reserve').val());
if((BuyItNowPrice <= StartingPrice) && (StartingPrice > 0)){
alert("The 'Buy It Now' price must be higher...");
return false;
}
if((Reserve <= StartingPrice) && (StartingPrice > 0)){
alert("Your 'Reserve Price' must be higher...");
return false;
}
return true;
}
}
Question: How do I call it on blur? I tried this code below but it doesn't seem to work:
$('#StartingPrice').blur(function(){
checkStartPrice();
});
This is the correct way to call it.
The only reason it may fail is that the #StartingPrice element does not exist at the time of the .blur() call.
If it is present in the page, use this:
$(document).ready(function() {
$('#StartingPrice').blur(checkStartPrice)
})
If it is dynamically added via AJAX, use this:
$(document).ready(function() {
$('#StartingPrice').live('blur',checkStartPrice)
})
Note that the second solution requires at least jQuery 1.4.1

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