Function isArray

Returns whether x is an array.

We have this because Array.isArray(x) returns x is any[], which means that this code compiles without error, for example:

function thisShouldNotCompile(x: string | readonly string[]) {
    if (Array.isArray(x)) {
        const s = x[0];
        s.thisIsAnAny("but it's actually a string");
    }
}
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Returns whether x is an array.

We have this because Array.isArray(x) returns x is any[], which means that this code compiles without error, for example:

function thisShouldNotCompile(x: string | readonly string[]) {
    if (Array.isArray(x)) {
        const s = x[0];
        s.thisIsAnAny("but it's actually a string");
    }
}
Copy