What dose it mean using [...parent.path !] . the?

Question

I go over the angular form module and I saw a syntax I don't recognize [...parent.path !, name];

is it typescript syntax?

it can be found at this link which is angular github code.

https://stackoverflow.com/questions/42273853/in-typescript-what-is-the-exclamation-mark-bang-operator-when-dereferenci — Radonirina Maminiaina, Mar 23 '18 at 08:43
`...` is the spread operator, and ! indicates to the compiler that the object won't be null — David, Mar 23 '18 at 08:44

score 3 · Accepted Answer · answered Mar 23 '18 at 08:46

As indicate here.

A new ! post-fix expression operator may be used to assert that its operand is non-null and non-undefined in contexts where the type checker is unable to conclude that fact. Specifically, the operation x! produces a value of the type of x with null and undefined excluded. Similar to type assertions of the forms <T>x and x as T, the ! non-null assertion operator is simply removed in the emitted JavaScript code.

// Compiled with --strictNullChecks
function validateEntity(e?: Entity) {
    // Throw exception if e is null or invalid entity
}

function processEntity(e?: Entity) {
    validateEntity(e);
    let s = e!.name;  // Assert that e is non-null and access name
}

It indicates non-null value.

What dose it mean using [...parent.path !] . the?

1 Answers1