What does ? and : within an expression?

Question

I saw on a website the following code:

var campo1 = document.getElementById('valor1').value;
var campo2 = document.getElementById('valor2').value;

var maior = (parseFloat(campo1) > parseFloat(campo2) ? campo1 : campo2);
var menor = (parseFloat(campo1) < parseFloat(campo2) ? campo1 : campo2);

My question is, what does the placement of: >, <, ? and :, within these variables.

Answer 1

The ternary Operator

 a ? b : c

"If a is true, returns b, else it returns c"

Let’s look at the example given:

 var maior = (parseFloat(campo1) > parseFloat(campo2)? campo1 : campo2);

The < and > are the largest and smallest comparators you should already know. What is perhaps a novelty there is the ternary operator, delimited by ? and :

In this case, the comparison is first resolved parseFloat(campo1) > parseFloat(campo2). If the result of this comparison is true, the variable maior will receive the value of campo1. Otherwise, you will receive the value of campo2.

It is equivalent to the IF inline (or IIF) of some languages:

// Linguagem com operador ternário
print A > 10 ? "A é maior que dez" : "A é menor que dez"

// Linguagem com if inline
print if( A > 10, "A é maior que dez", "A é menor que dez" )

Answer 2

It’s a tender squeeze of a check.

The syntax is: conditional ? true : false.

Or: "se isso retornar true" ? "retorne isso" : "se não, retorne isso".

In your case, in the variable maior you are checking whether parseFloat(campo1) is greater than (>) parseFloat(campo2), if so, the value of the variable maior becomes the value of the variable campo1, otherwise becomes the variable value campo2 and so on.

It would be the same as:

if(parseFloat(campo1) > parseFloat(campo2)) {
    var maior = campo1;
} else {
    var maior = campo2;
}

But in summary form.

Answer 3

Ternary conditional operator

There is in javascript an operator that looks like an if/Else, which serves to return a value given a condition. This operator is a ternary conditional operator (meaning that it has three operands). Its form is as follows::

condicao ? parte_verdadeira : parte_falsa;

If the condition is evaluated as true, the expression returns to parte_verdadeira, otherwise returns to parte_falsa.

Example:

var x = valor > 10 ? "maior que 10" : "menor ou igual a 10";

Expression evaluated as true: condicao

The condition is any expression that can be evaluated as true or false. Note that I did not say "is true" but "can be evaluated as true". Said this way, because there are several values that are not true/false, but can be evaluated as such:

• 0 is rated as false, and other numbers as true
• null and Undefined are evaluated as false
• empty string is false, any other string is true

About your doubt

The signs of < and > are only comparators being used in the ternary operator’s condition part.

Answer 4

It’s called IF TERNARY

for example:

var maior = (parseFloat(campo1) > parseFloat(campo2)? campo1 : campo2);

is the same as

maior="";
if((parseFloat(campo1) > parseFloat(campo2))
{
  maior=campo1;
}else{
  maior=campo2;
}

or after the ? it performs if the condition is true and the : is if she’s fake

more details: http://msdn.microsoft.com/pt-br/library/be21c7hw(v=vs.94). aspx

Answer 5

Simple, this is nothing more than if and Else in a fast way When parseFloat(field1) > parseFloat(field2), if true, the variable takes field1, otherwise it will be field2.

There is still x ?? y, where if x is different from null x otherwise y.