TypeScript. It evaluates its left-hand operand and, if the result value

is not "nullish" (null or undefined), takes that value as its result;

otherwise, it evaluates the right-hand operand and takes the resulting

value as its result.

In the following example, a will be assigned the value of b if the value

of b is not null or undefined, otherwise it will be assigned 3.

const a = b ?? 3;

Before the nullish coalescing operator, programmers would use the

logical OR operator (||). But where ?? looks specifically for null or

undefined, the || operator looks for any falsy value: null, undefined,

"", 0, NaN, and of course, false.

In the following example, a will be assigned the value of b if the value

of b is truthy, otherwise it will be assigned 3.

const a = b || 3;

A pair of curly brackets { } and an enclosed sequence of statements

constitute a compound statement, which can be used wherever a statement

can be used.

if (expr) {

//statements;

} else if (expr2) {

//statements;

} else {

//statements;

}

The conditional operator creates an expression that evaluates as one of

two expressions depending on a condition. This is similar to the if

statement that selects one of two statements to execute depending on a

condition. I.e., the conditional operator is to expressions what if is

to statements.

const result = condition ? expression : alternative;

is the same as:

if (condition) {

const result = expression;

} else {

const result = alternative;

}

Unlike the if statement, the conditional operator cannot omit its

"else-branch".

The syntax of the JavaScript switch statement is as follows:

switch (expr) {

case SOMEVALUE: