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https://github.com/ciricc/tst-defaults
Make your TypeScript defaults expectable with tst-reflect and ttypescript
https://github.com/ciricc/tst-defaults
defaults reflect reflection ttypescript types typescript
Last synced: 9 days ago
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Make your TypeScript defaults expectable with tst-reflect and ttypescript
- Host: GitHub
- URL: https://github.com/ciricc/tst-defaults
- Owner: ciricc
- License: mit
- Created: 2022-06-10T00:05:07.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2022-07-04T17:30:17.000Z (over 2 years ago)
- Last Synced: 2024-09-14T10:12:37.360Z (about 2 months ago)
- Topics: defaults, reflect, reflection, ttypescript, types, typescript
- Language: TypeScript
- Homepage:
- Size: 226 KB
- Stars: 3
- Watchers: 2
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Make your defaults expectable
This project uses [tst-reflect](https://github.com/Hookyns/tst-reflect) library for making your schemas expectable. For example, if you are parsing JSON with predefined schema but didn't want to check that some fields is not defined in object and want to just get default values.
## Simple example
This simple example shows how much problems we have when parsing JSON in TypeScript.
```ts
type JSONSchema = {
n: number
level: {
n2: number
bool: boolean
},
list: number[],
b: boolean
}
const parsedJson = JSON.parse('{}') as JSONSchema;
console.log(parsedJson.level.n2 + 1) // error, level is undefined
console.log(parsedJson.list.map(el => el + 1)) // error, list is undefined and has no method map
console.log(parsedJson.n + 1) // NaN
if (parsedJson.b) { // it may have error, because undefined is not a false
makeRiskCall()
}
if (paredJson.b === true) { // why we need this in TypeScript?? So much code...
makeRiskCall()
}
```
But you may say that we have a solution?
```ts
class JSONSchema {
public n: number = 0;
public level: {
n2: number
bool: boolean
} = {
n2: 0,
bool: false,
}
public list: number[] = [];
public b:boolean = false;
constructor(v:any) {
Object.assign(this, v);
}
}
const parsedJson = new JSONSchema(JSON.parse('{"level": {"n2": 1}}'));
console.log(parsedJson.n + 1) // ok
console.log(parsedJson.level.n2 + 1) // ok, result is 2
console.log(parsedJson.level.bool) // undefined
```
Not so bad, but still not good. And we have much code again.
## Solution
```ts
import { mergeDefaults } from "tst-defaults";
type JSONSchema = {
n: number
level: {
n2: number
bool: boolean
},
list: number[],
b: boolean
}
const parsedJson = mergeDefaults(JSON.parse('{"level":{"bool":true}}'));
console.log(parsedJson.b === false) // ok
console.log(parsedJson.list.map(el => el + 1)) // ok
console.log(parsedJson.level.n2 + 1 === 1) // ok
console.log(parsedJson.level.bool == true) // ok
console.log(parsedJson.n + 1) // ok
```
Simple and fast.
## Installation
```shell
yarn add --dev typescript ttypescript tst-reflect-transformer ts-node
```
```shell
yarn add tst-defaults
```
Setup your `tsconfig.json`
```js
{
"ts-node": {
"compiler": "ttypescript"
},
"compilerOptions": {
...,
"plugins": [
{
"transform": "tst-reflect-transformer"
}
]
}
}
```
Setup `package.json`
```json
{
"scripts": {
"start": "ts-node index.ts",
"build": "ttsc"
}
}
```
## API
Some api documentation.
### useDefault
Saves type default value in storage for next time resolving.
```ts
import { useDefault, mergeDefaults } from 'tst-defaults';
type Duration = {
seconds: number;
};
type Schema = {
expires: Duration;
options: Object;
users: number;
};
useDefault({ seconds: -1 });
const config = mergeDefaults(JSON.parse('{}'));
console.log(config.expires); // { seconds: -1}
console.log(config.users); // 0
console.log(config.options); // {}
```
### mergeDefaults
Merging default values into variable value. If variable is undefined, than it will create default value for it.
```ts
import { mergeDefaults } from "tst-defaults";
const jsonErrorIgnored = ():any => {}
type Schema = {
n: number
};
const config = mergeDefaults(jsonErrorIgnored());
console.log(config.n) // 0, config is created as object
```
### getDefaultValue
Returns default value for type.
```ts
import { getDefaultValue } from "tst-defaults";
console.log(getDefaultValue()) // ""
enum Person {
UNKNOWN = 0,
PRIVATE = 1,
PUBLIC = 2,
}
console.log(getDefaultValue()) // ""
console.log(getDefaultValue()) // false
console.log(getDefaultValue()) // {}
console.log(getDefaultValue()) // 0
console.log(getDefaultValue>()) // []
console.log(getDefaultValue()) // null
console.log(getDefaultValue() == Person.UNKNOWN) // true
```
### deleteDefault
Removes type default value from storage.
```ts
import { deleteDefault, useDefault, getDefaultValue } from "tst-defaults";
type Duration = {
seconds: number;
};
useDefault({
seconds: -1
});
console.log(getDefaultValue();) // {seconds: -1}
deleteDefault();
console.log(getDefaultValue();) // {}
```