The if statement not working properly in Javascript

Question

I am trying to create a logic that if anyone enters "" and "" characters inside <textarea>, then only Jquery should show the win message.I have a textarea with class html, a h2 with class result which shows win or loss.By now, I have this code:

var html = $('.html').val();
if(html.indexOf("</p>" && "<p>") === -1)
{
document.getElementById("result").innerHTML = "You lost it.";
}
else{
document.getElementById("result").innerHTML = "Hurray!You won";
}

But, this code is only checking if the  is there and not checking for .So what can I do....

html.indexOf("" && "") - is that valid to have && <expr> inside indexOf? — tymeJV
– tymeJV, Commented Sep 10, 2014 at 16:17
"" && "" === "", you'll need to check both and then compare results. — Teemu
– Teemu, Commented Sep 10, 2014 at 16:17
@tymeJV Yes it is, as long as the result of expression(s) can be evaluated to a string. — Teemu
– Teemu, Commented Sep 10, 2014 at 16:23

Barmar · Accepted Answer · 2014-09-10 16:24:58Z

5

The expression "" && "" is equivalent to "" -- && evaluates each of its arguments from left to right, and returns the last truthy argument. Since both strings are truthy, what you wrote is effectively:

if (html.indexOf("<p>") === -1)

If you want to test whether a string contains two substrings, you have to call indexOf separately for each of them:

if (html.index("</p>") !== -1 && html.indexOf("<p>") !== -1)

edited Sep 10, 2014 at 16:24

answered Sep 10, 2014 at 16:18

Barmar

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1 Comment

LalaByte Over a year ago

oh @Barmar.I can't get the way to thnx you more than saying it you here.Thnq very much.

lordstyx · Accepted Answer · 2014-09-10 16:17:56Z

2

From MDN (Logical Operators) - Logical And (&&):

Returns expr1 if it can be converted to false; otherwise, returns expr2. Thus, when used with Boolean values, && returns true if both operands are true; otherwise, returns false.

 isn't being evaluated as false, so the second value is returned which is .

This means that you're only checking for the index of . Try this instead:

var html = $('.html').val();
if (html.indexOf("</p>") === -1 && html.indexOf("<p>") === -1) {
    document.getElementById("result").innerHTML = "You lost it.";
}
else {
    document.getElementById("result").innerHTML = "Hurray! You won";
}

answered Sep 10, 2014 at 16:17

lordstyx

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Comments

Tom Fenech · Accepted Answer · 2014-09-10 16:17:40Z

1

.indexOf takes a single string as an argument. You cannot combine string elements together using && like that.

The simplest way to modify your code would be to make two separate checks, one for the opening tag and one for the close:

if (html.indexOf("</p>") !== -1 && html.indexOf("<p>") !== -1)

This makes two separate checks for the two strings.

Alternatively, you could create a jQuery object from the HTML fragment inside your <textarea>, then check that it has no children that are  tags:

if ($('<div>'+html+'</div>').find('p').length > 0) {
    // the textarea contains some <p> tags
}

answered Sep 10, 2014 at 16:17

Tom Fenech

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