Ternary Operators in JavaScript Without an "Else"

Ternary operators in JavaScript without an else

First of all, a ternary expression is not a replacement for an if/else construct - it's an equivalent to an if/else construct that returns a value. That is, an if/else clause is code, a ternary expression is an expression, meaning that it returns a value.

This means several things:

• use ternary expressions only when you have a variable on the left side of the = that is to be assigned the return value
• only use ternary expressions when the returned value is to be one of two values (or use nested expressions if that is fitting)
• each part of the expression (after ? and after : ) should return a value without side effects (the expression x = true returns true as all expressions return the last value, but it also changes x without x having any effect on the returned value)

In short - the 'correct' use of a ternary expression is

var resultofexpression = conditionasboolean ? truepart: falsepart;

Instead of your example condition ? x=true : null ;, where you use a ternary expression to set the value of x, you can use this:

 condition && (x = true);

This is still an expression and might therefore not pass validation, so an even better approach would be

 void(condition && x = true);

The last one will pass validation.

But then again, if the expected value is a boolean, just use the result of the condition expression itself

var x = (condition); // var x = (foo == "bar");

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UPDATE

In relation to your sample, this is probably more appropriate:

defaults.slideshowWidth = defaults.slideshowWidth || obj.find('img').width()+'px';

If without else ternary operator

No, you cannot do that.
Instead try this:

if(bool1 && bool2) voidFunc1();

Javascript Ternary operator with empty else

Answer to your real question in the comments:

all2.forEach(function (e) {
    e.getAttribute("class") && only.push(e.getAttribute("class"));
});

Conditional (ternary) operator is going directly to else option

let tipoUser = parseInt(sessionStorage.getItem("TipoUser"))

How do you use the ? : (conditional) operator in JavaScript?

This is a one-line shorthand for an if-else statement. It's called the conditional operator.¹

Here is an example of code that could be shortened with the conditional operator:

var userType;
if (userIsYoungerThan18) {
  userType = "Minor";
} else {
  userType = "Adult";
}

if (userIsYoungerThan21) {
  serveDrink("Grape Juice");
} else {
  serveDrink("Wine");
}

This can be shortened with the ?: like so:

var userType = userIsYoungerThan18 ? "Minor" : "Adult";

serveDrink(userIsYoungerThan21 ? "Grape Juice" : "Wine");

Like all expressions, the conditional operator can also be used as a standalone statement with side-effects, though this is unusual outside of minification:

userIsYoungerThan21 ? serveGrapeJuice() : serveWine();

They can even be chained:

serveDrink(userIsYoungerThan4 ? 'Milk' : userIsYoungerThan21 ? 'Grape Juice' : 'Wine');

Be careful, though, or you will end up with convoluted code like this:

var k = a ? (b ? (c ? d : e) : (d ? e : f)) : f ? (g ? h : i) : j;

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¹ Often called "the ternary operator," but in fact it's just a ternary operator [an operator accepting three operands]. It's the only one JavaScript currently has, though.

JavaScript shorthand if statement, without the else portion

you can use && operator - second operand expression is executed only if first is true

direction == "right" && slideOffset += $(".range-slide").width()

in my opinion if(conditon) expression is more readable than condition && expression

How to not return a value from the last ternary operator?

How to not return a value from the last ternary operator?

No, you can't, the last part of a ternary operator is required. To accomplish that, you need if-else blocks.

if (col_1 === 0) {
    result = 0;
} else if (col_1 >= 1) {
    result = col_1 - 1;
}

An alternative is using the logical operator &&

Like I said, the last part is required

(col_1 === 0) ? 0 : (col_1 >= 1 && col_1 - 1);

var col_1 = 0;var result = (col_1 === 0) ? 0 : (col_1 >= 1 && col_1 - 1);console.log(result);
col_1 = 5;result = (col_1 === 0) ? 0 : (col_1 >= 1 && col_1 - 1);console.log(result);
col_1 = 3;result = (col_1 === 0) ? 0 : (col_1 >= 1 && col_1 - 1);console.log(result);
col_1 = -1;result = (col_1 === 0) ? 0 : (col_1 >= 1 && col_1 - 1); // This case will always return false because 'col_1 < 0' // Here you can check for that valueconsole.log("You need to check this situation: ", result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Is it possible to write one way ternary operator?

I guess you could do something like:

function sumFibs(num) {
    let a = 0, b = 1, fib = 0; 
    let i = 0; 
    let fibArr = []
    let result = 0; 

    while(fib <= num){
        fibArr.push(fib)
        a = b; 
        b = fib; 
        fib = a+b; 
    }

    for(let i = 0; i<fibArr.length; i++) {
        (fibArr[i] % 2 !== 0) ? (result += fibArr[i]) : null;
    }
    console.log(result)
    return result; 
}

But this doesn't seem to add much value, only confusion. Note that ternary operator is often used as an assignment, not a control flow statement.

To be more specific this is the part that was changed. Note that there is no way of having something like {condition} ? value : syntax wise. You always have to return an expression after the colon.

(fibArr[i] % 2 !== 0) ? (result += fibArr[i]) : null;

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