How do I test if a variable does not equal either of two values?

I want to write an if/else statement that tests if the value of a text input does NOT equal either one of two different values. Like this (excuse my pseudo-English code):

var test = $("#test").val();
if (test does not equal A or B){
    do stuff;
}
else {
    do other stuff;
}

How do I write the condition for the if statement on line 2?

Solution 1:

Think of ! (negation operator) as "not", || (boolean-or operator) as "or" and && (boolean-and operator) as "and". See Operators and Operator Precedence.

Thus:

if(!(a || b)) {
  // means neither a nor b
}

However, using De Morgan's Law, it could be written as:

if(!a && !b) {
  // is not a and is not b
}

a and b above can be any expression (such as test == 'B' or whatever it needs to be).

Once again, if test == 'A' and test == 'B', are the expressions, note the expansion of the 1st form:

// if(!(a || b)) 
if(!((test == 'A') || (test == 'B')))
// or more simply, removing the inner parenthesis as
// || and && have a lower precedence than comparison and negation operators
if(!(test == 'A' || test == 'B'))
// and using DeMorgan's, we can turn this into
// this is the same as substituting into if(!a && !b)
if(!(test == 'A') && !(test == 'B'))
// and this can be simplified as !(x == y) is the same as (x != y)
if(test != 'A' && test != 'B')

Solution 2:

ECMA2016 Shortest answer, specially good when checking againt multiple values:

if (!["A","B", ...].includes(test)) {}

Solution 3:

In general it would be something like this:

if(test != "A" && test != "B")

You should probably read up on JavaScript logical operators.

Solution 4:

I do that using jQuery

if ( 0 > $.inArray( test, [a,b] ) ) { ... }

Solution 5:

var test = $("#test").val();
if (test != 'A' && test != 'B'){
    do stuff;
}
else {
    do other stuff;
}