ts-json-checker

ts-json-checker is type check function generator from type assertion for TypeScript.

It is mainly used for JSON input check.

Feature

• Generate type check function for JSON.parsed object

• Custom convert for specified type

• No required library at runtime

Environment

• Node.js 10
• TypeScript 3.3.3333

Install

npm install --save-dev ts-json-checker

Configure

ts-json-config.ts (default file name)

import { generate, convert } from 'ts-json-checker'

// output file name
const fileName = './generated.ts'

export interface Item {
    name: string
    price: number
    releaseDate: Date
}

// string to Date type convertion
convert<Date>(v => {
    if (v instanceof Date) return v
    const dt = typeof v === "string" ? Date.parse(v) : NaN
    if (isNaN(dt)) throw new TypeError('Unable to convert to date. value: ' + v)
    return new Date(dt)
})

// generate Item type check function
generate<Item>("parseItem")

// generate Array of Item type check function
generate<Item[]>("parseItems")

// union type
generate<Item | null>("parseUnion")

more config sample

Usage

Command Lines:

Usage: ts-json-checker [options]

Options:
  -v, --version               output the version number
  -c, --config <config-file>  specify config file
  -n, --linefeedNewLine       set new line chars to linefeed(LF)
  -h, --help                  output usage information

example:

# use default config file name 'ts-json-config.ts'
npx ts-json-checker

# specify config file name
npx ts-json-checker --config ./other-ts-json-config.ts

Output

generated.ts

export interface Item {
    name: string;
    price: number;
    releaseDate: Date;
}

export function parseItem(v: any): Item {
    if (v !== null && typeof v === "object")
        __check_1(v, "v");
    else
        throw new TypeError("v is not Object.");
    return <Item>v;
}

export function parseItems(v: any): Item[] {
    if (Array.isArray(v))
        for (let i = 0; i < v.length; i++)
            if (v[i] !== null && typeof v[i] === "object")
                __check_1(v[i], "v[" + i + "]");
            else
                throw new TypeError("v[" + i + "] is not Object.");
    else
        throw new TypeError("v is not Array.");
    return <Item[]>v;
}

export function parseUnion(v: any): Item | null {
    if (v === null) { }
    else if (v !== null && typeof v === "object")
        __check_1(v, "v");
    else
        throw new TypeError("v is not Null | Object.");
    return <Item | null>v;
}

function __check_1(v: any, r: string) {
    if (typeof v.name === "string") { }
    else
        throw new TypeError(r + ".name is not String.");
    if (typeof v.price === "number") { }
    else
        throw new TypeError(r + ".price is not Number.");
    v.releaseDate = __convert_1(v.releaseDate);
}

function __convert_1(v: any): Date {
    if (v instanceof Date)
        return v;
    const dt = typeof v === "string" ? Date.parse(v) : NaN;
    if (isNaN(dt))
        throw new TypeError('Unable to convert to date. value: ' + v);
    return new Date(dt);
}