How to use null and undefined in Typescript

This article mainly introduces how to use null and undefined in Typescript. It is very detailed and has a certain reference value. Friends who are interested must finish it!

Null and undefined

In javascript, null means "nothing", is a special type with only one value, represents an empty object reference, and undefined represents a variable with no set value.

By default, null and undefined are subtypes of all types, which means you can assign null and undefined to variables of type number

Let num:number | undefined; / / numeric type or undefinedconsole.log (num); / / correct num = 123; console.log (num); / / correct

But ts is configured with strictNullChecks tags, and null and undefined can only be assigned to void and each of them.

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