Menu
Equality operators: == and != The result type for these operators is bool . The equal-to operator ( == ) returns true if both operands have the same value; otherwise, it returns false . The not-equal-to operator ( != ) returns true if the operands don't have the same value; otherwise, it returns false .
The strict equality operator ( === ) checks whether its two operands are equal, returning a Boolean result. Unlike the equality operator, the strict equality operator always considers operands of different types to be different.
A variable holds more than one value if you declare it to be of a composite data type. Composite Data Types include structures, arrays, and classes. A variable of a composite data type can hold a combination of elementary data types and other composite types. Structures and classes can hold code as well as data.
The strict inequality operator ( !== ) checks whether its two operands are not equal, returning a Boolean result. Unlike the inequality operator, the strict inequality operator always considers operands of different types to be different.
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')
ECMA2016 Shortest answer, specially good when checking againt multiple values:
if (!["A","B", ...].includes(test)) {}
In general it would be something like this:
if(test != "A" && test != "B")
You should probably read up on JavaScript logical operators.
I do that using jQuery
if ( 0 > $.inArray( test, [a,b] ) ) { ... }
var test = $("#test").val();
if (test != 'A' && test != 'B'){
do stuff;
}
else {
do other stuff;
}
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With