Note: JavaScript Notes a ? b : c

I often see a ? b : c in JavaScript source code, but I don't quite understand it, so I looked it up specifically.

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In JavaScript, ? and : are a pair of operators, known as 'logical non' and 'logical or' (logical or).

a ? b : c is a ternary operator used to simplify if-else statements. Its working principle is:

• If the expression a is a truthy value, execute and return the expression b
• If the expression a is a falsy value, execute and return the expression c

Therefore, the if-else statement equivalent to a ? b : c is:

if ( a ) {
  return b;
} else {
  return c;
}

Both methods can achieve the same logic, but the first method uses the ternary operator, and the second method uses the if-else statement.

In JavaScript, the ? and : operators are not only used for logical operations but can also be used in other scenarios, such as:

• a ? b : c can be used as a conditional expression to simplify if-else statements.
• a & b | c can be used as a bitwise operation for multiple assignments.
• a & b ^ c can also be used as a bitwise operation.

In summary, the ? and : operators are a powerful shorthand tool in JavaScript, helping to improve code efficiency and readability.