iskm/learnxinyminutes-docs
1
0
Fork 0
mirror of https://github.com/adambard/learnxinyminutes-docs.git synced 2025-04-26 23:23:55 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Merge pull request #3694 from davidgtu/ts/type-assertion

Browse Source 
[en/typescript] add type assertion section
This commit is contained in:
Divay Prakash 2020-01-11 14:23:22 +05:30 committed by GitHub
commit a6c71dae3d
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 16 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
typescript.html.markdown
View File

@ -257,8 +257,24 @@ for (const i in list) {
console.log(i); // 0, 1, 2
}
// Type Assertion
let foo = {} // Creating foo as an empty object
foo.bar = 123 // Error: property 'bar' does not exist on `{}`
foo.baz = 'hello world' // Error: property 'baz' does not exist on `{}`
// Because the inferred type of foo is `{}` (an object with 0 properties), you
// are not allowed to add bar and baz to it. However with type assertion,
// the following will pass:
interface Foo {
bar: number;
baz: string;
}
let foo = {} as Foo; // Type assertion here
foo.bar = 123;
foo.baz = 'hello world'
```