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Use if-loop to calculate price depending on the input in js

I'm pretty new to Javascript and React, so please bear with me.
I have a component in my app, that is taking a timespan from the user, but now I want to calculate the price the user would have to pay, depending on their input. I figured that it would probably be the easiest way to use an if loop but something is very off with that and I am a little stuck.
Is my attempt okay in general or does it need a separate function that I have to call in order to do what I want to do?
onConfirm(hour, minute) {
this.setState({ time: `Dauer: ${hour}:${minute}` });
this.setState(if((hour) < 4){return price = `Preis: (${hour}* 1.5) €`;}
else {return price= 'Preis: 5.50 €';} );
this.TimePicker.close();
}

Within an object literal, you can't use statements, only expressions. if is a statement.
If you want to do that either/or logic in an expression, you use the conditional operator (? :), like this:
onConfirm(hour, minute) {
this.setState({
time: `Dauer: ${hour}:${minute}`,
price: hour < 4 ? `Preis: (${hour}* 1.5) €` : 'Preis: 5.50 €'
});
this.TimePicker.close();
}
The conditional operator expression in the above is:
hour < 4 ? `Preis: (${hour}* 1.5) €` : 'Preis: 5.50 €'
It's a ternary operator (an operator accepting three operands):
The condition to test (hour < 4)
The expression to evaluate if the condition is truthy¹ (`Preis: (${hour}* 1.5) €`)
The expression to evaluate if the condition is falsy¹ ('Preis: 5.50 €')
Also note you had a closing ' on a template literal (needed a backtick instead).
¹ "truthy" and "falsy" - JavaScript implicitly converts (or coerces) values. When you use a value as a test, such as in an if or a conditional operator, JavaScript converts the value you provide to a boolean value (true or false). Values that convert to true are called "truthy" values, ones that convert to false are called "falsy." The falsy values are NaN, null, undefined, 0, "", and of course false (on browsers, document.all is also falsy for various reasons I explain in my book). All other values are truthy.

what is the meaning of +!! in javascript?

I came across this line of code recently, and want to understand what it means and does, as my javascript-foo is not that hot :
if ((+!!config.template) + (+!!config.templateUrl) !== 1) {}
from what I can gather, it is checking to see if either option is set (so either template, or templateUrl must be set, not both or none)
so, if config.template was set,
+config.template would not work (template is not a number)
!config.template would return false (-1)
!!config.template would return true (0)
+!!config.template would therefore return 1
if config.template was not set,
!config.template would return true (0)
!!config.template would return false (-1)
+!!config.template would therefore return 0
if then you were to apply the same to config.templateUrl , you would end up with 1 if set, 0 if not
So the final test is to see if the sum of config.template and config.templateUrl is 1 (ie one or the other is set)
Is this valid reasoning ?

The bool value is being cast to a Number by prepending it with +.
!! in the code above is checking for existence of the property template on config. If there is no template found !! would usually return false, however by prepending +, it returns 0. Both +!! statements return numbers, which when they're added together will either be 0 or 1.
The final check will return true if both or none were set / true (!== 1)

Best way to convert result of .indexOf to a Boolean using JavaScript or jQuery

I was wondering, say I had some thing like the following:
console.log(element.find('div').eq(3).text().indexOf('whatever'));
bearing in mind that element is defined and the console is logging a value of 32 (or anything that isn't -1) what would be the best way of converting the result into a Boolean so my console.log either outputs true or false
Thanks in advance.

The answer above will work, however if you are as nerdy as I, you will far prefer this:
console.log(~element.find('div').eq(3).text().indexOf('whatever'));
The obscure '~' operator in javascript performs the operation "value * -1 - 1", e.g. ~-2 === 1. The only use case I have ever had for this is in converting the "not found" -1 from ".indexOf()" into "0" (a falsey value in javascript), follow through and see it will convert an index found at position "0" to "-1", a truthy value.
tldr:
~[1,2,3].indexOf(0) // => 0
!!~[1,2,3].indexOf(0) // => false
~[1,2,3].indexOf(1) // => -1
!!~[1,2,3].indexOf(1) // => true

console.log(element.find('div').eq(3).text().indexOf('whatever') > -1);

how to simplify my conditional statement?

I am trying to simplify the following codes. The codes seem to redundant to me. Are there anyone here can help me out? Thanks a lot!
if(area.regionCode=='0' || area.regionCode==null){
var fakecode=area.region.substring(0, area.region.length - 1);
area.region= fakecode +i;
}

Whenever you think some code is not directly revealing, try giving it a new home with a suitable name:
if (!isValidRegionCode(area.regionCode)) {
...
}
...
function isValidRegionCode(regionCode) {
return area.regionCode != null && area.regionCode != '0';
}
It has more code overall, but makes your intentions clear.

if(parseInt(area.regionCode) > 0) {}

I would recommend explicit condition checks. When using:
if (area.regionCode) { }
Style of logic, one is treating varAny as a boolean value. Therefore, JavaScript will perform an implicit conversion to a boolean value of whatever object type varAny is.
or
if(Boolean(area.regionCode)){
codes here;
}
both will work same
returns false for the following,
null
undefined
0
""
false.
beware returns true for string zero "0" and whitespace " ".
you can also first trim the output so " " issue will be solve
here tutorial How do I trim a string in javascript?
in the #mttrb and #nnnnnn described case you can first convert string to either int or float by parseInt() and parseFloat() check this Converting strings to numbers

What's the difference between & and && in JavaScript?

What's the difference between & and && in JavaScript?
Example code:
var first = 123;
var second = false;
var third = 456;
var fourth = "abc";
var fifth = true;
alert(first & second); // 0
alert(first & third); // 72
alert(first & fourth); // 0
alert(first & fifth); // 1
alert(first && second); // false
alert(first && third); // 456
alert(first && fourth); // abc
alert(first && fifth); // true
It seems like && is a logical and which gives me always the second value if both are true.
But what is &?
(By the way, && seems to be and in Python; & seems to be & in Python)

& is bitwise AND
This operator is almost never used in JavaScript. Other programming languages (like C and Java) use it for performance reasons or to work with binary data. In JavaScript, it has questionable performance, and we rarely work with binary data.
This operator expects two numbers and retuns a number. In case they are not numbers, they are cast to numbers.
How does it work? Wikipedia has an answer: https://en.wikipedia.org/wiki/Bitwise_operation#AND
&& is logical AND
Most usually, programmers use this operator to check if both conditions are true, for example:
true && true // returns true
true && false // returns false
However, in JavaScript, it is extended to allow any data type and any number of terms. It returns:
First term that evaluates to false
Last term otherwise (if all are true-y)
Here are some examples:
true && false && true // returns false
true && 20 && 0 && false // returns 0 (it is first false-y)
10 && "Rok" && true && 100 // returns 100 (as all are true-y)
&& short-circuiting
As can be seen from above, as soon as you find one that term is false-y, you needn't to care about the following terms. This allows Javascript to stop evaluation altogether. This is called short circuiting.
This statement doesn't alert anything and false is returned:
true && false && alert("I am quiet!") // returns false
Therefore, you could use the && operator as a shorter replacement for an if statement. These are equivalent:
if (user.isLoggedIn()) alert("Hello!")
user.isLoggedIn() && alert("Hello!")
Almost all JS compressors use this trick to save 2 bytes.

& is the bitwise "and". This means that if you have two numbers converted to binary, the result is a number that has the 1 digit at the positions where both numbers have 1.
100011 //35
& 111001 //57
---------
100001 //35 & 57 == 33

To determine whether two boolean values put together are true or false, if you want to check them both (like validation on the web page), you may use the & operator. & is bitwise AND.
With the && operator, once it finds the first value is false, it will end evaluation and not to check the second value.

With all the lofty, detailed insights throughout, they have mostly missed the truth that there is a conditional evaluation where ONLY the single & will work. The practical layman's answer that solved my head beating on an IF statement string of MULTIPLE chained && each !== to a condition was causing FAILURE and needed to legitimately use the single &. I thank Jake Wayne (and Russ) for their unfairly downvoted answer that got it right given that where there is more than one && that !== it has already ceased its evaluation and proceeds no further after the first evaluation is found ==!. With the && it thinks its job is done after the first evaluation shows !== [eg. false]. My failing code was
IF ((sessionStorage.myLable !== "LableStringA") && (sessionStorage.myLable !== "LableStringB") && (sessionStorage.myLableZ !== "LableStringA") && (sessionStorage.myLableZ !== "LableStringB")) { ...)
Here, properly substituting and using a single & for the && it was both practically in the real world and technically the correct answer. Thank you again Jake Wayne (and Russ) for the insight and understanding of code.