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Eckehard
Eckehard

Posted on • Updated on

Nano "Typescript" without compilation

#javascript #typescript #programming

Thanks to this post from Toby Farley (Shadow Chicken), I had an inspiration to build my own tiny little nano "typescript" running without compilation.

Ok, typescript provides much more, but if you only need some typechecks, this little routine would do the trick:

/* ==================================================
    Nano typeCheck
    Valid types
    "var": Variant - all types allowed 
    "string"
    "number"
    "bigInt"
    "boolean"
    "object"
    "array"
    "date"
    "set"
    "function"
  ================================================== */
  function typeCheck(v) {
  if ((typeof v) !== "object") throw (`Parameter must be Object in function ${typeCheck.caller.name}`)

  // Build return value array
  let res = Object.entries(v).map((a, i) => {
    let [typ, val] = a;  // get key/values
    typ = typ.charAt(0).toUpperCase() + typ.slice(1) // Capitalize
    if (typ === "Var")  // Variant type
      return val
    if (val.constructor.name !== typ) // check type
      throw (`Type error parameter ${i + 1} is not ${typ} in function ${typeCheck.caller.name}`)
    return (val)
  })
  return res
}

function myFunc(a,b,c,d) {
  typeCheck({ string: a, boolean: b, array: c, var: d })
  console.log(a)
  console.log(b)
  console.log(c)
  console.log(d)
}

myFunc( "5",  true, [1, 2, 3, 4, 5], "Do what you want")
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You can also submit typ declaration with the parameters like this:

function myFunc(pars) {
  let [a, b, c, d] = typeCheck(pars)
  console.log(a)
  console.log(b)
  console.log(c)
  console.log(d)
}

myFunc({ string: "5", boolean: true, array: [1, 2, 3, 4, 5], var: "Do what you want" })
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Types can be named using the standard type names with lower or upper case, so both would be accepted:

{ string: a, boolean: b, array: c, var: d }
{ String: a, Boolean: b, Array: c, Var: d }
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Tell me, what you think.

P.S.: This post was changed after the first sumbission to show different ways of usage.

Top comments (10)

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rudransh61 profile image
Rudransh Bhardwaj • • Edited

wow !!
this is awesome !!
I think it's already very great
you can add more unique features
it can be next big thing

nice

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artydev profile image
artydev •

Hy Eckehard, look at this :

for (let value of [
        "Array", "Boolean", "Date", "Element",
        "Error", "Function", "Map", "Node",
        "Number", "RegExp", "Set", "String",
        "Symbol", "Text"
    ]) Object.defineProperty(
        window[value].prototype, "__type", { value }
    );
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from Jason Knight DomJon

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efpage profile image
Eckehard •

Looks interesting, but - how to use it?

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artydev profile image
artydev • • Edited 
for (let value of [
        "Array", "Boolean", "Date", "Element",
        "Error", "Function", "Map", "Node",
        "Number", "RegExp", "Set", "String",
        "Symbol", "Text", "Object"
    ]) Object.defineProperty(
        window[value].prototype, "__type", { value }
);


let a =  []
let b = {}
let c = () => 1

console.log(a.__type)
console.log(b.__type)
console.log(c.__type)
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Look here demo

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efpage profile image
Eckehard •

Ok, this boils down to changing.

val.constructor.name
val.__type
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which is slightly faster. But most time in my initial routine is wasted capitalizing the keywords, which is just for convennience:

typ = typ.charAt(0).toUpperCase() + typ.slice(1) // Capitalize
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You can skip this line, if all types are written in uppercase.

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artydev profile image
artydev • • Edited

Eckehard,

Here is what Phind AI, propose for your code Demo:

for (let value of [
    "Array", "Boolean", "Date", "Element",
    "Error", "Function", "Map", "Node",
    "Number", "RegExp", "Set", "String",
    "Symbol", "Text"
]) {
    if (window[value]) { 
        Object.defineProperty(
            window[value].prototype, "__type", {
                value: value,
                writable: false, 
                enumerable: false, 
                configurable: false 
            }
        );
    }
}

function typeCheck(inputObject) {

    if (typeof inputObject !== "object") {
        throw new Error(`Parameter must be Object in function ${typeCheck.caller.name}`);
    }

    const checkedValues = Object.entries(inputObject).map(([typeKey, value], index) => {
        const capitalizedTypeKey = typeKey.charAt(0).toUpperCase() + typeKey.slice(1);
        if (capitalizedTypeKey === "Var") {
            return value;
        }
        const actualType = value.__type || typeof value;
        if (actualType !== capitalizedTypeKey) {
            throw new Error(`Type error parameter ${index + 1} is not ${capitalizedTypeKey} (expected ${capitalizedTypeKey}, got ${actualType}) in function ${typeCheck.caller.name}`);
        }
        return value;
    });

    return checkedValues;
}

function myFunc(pars) {
  let [a, b, c, d] = typeCheck(pars)
  console.log(a)
  console.log(b)
  console.log(c)
  console.log(d)
}

myFunc({ string: "5", boolean: true, array: [1, 2, 3, 4, 5], var: "Do what you want" })
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lexlohr profile image
Alex Lohr •

The main benefit of Typescript is that it catches type unsoundness in development without the need to add code to the production bundle.

Checking types in production is the field of scheme libraries. While your solution is interesting as an example, it cannot compete with scheme libraries like valibot or zod.

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efpage profile image
Eckehard •

Be serious: does it look like the next big thing? It's just an example, but I like the sceme....

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lexlohr profile image
Alex Lohr •

No, not really. I just wanted to point out that this is something different than TypeScript and that others have found a niche for similar solutions that even work very well together with TypeScript.

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artydev profile image
artydev •

Nice, but I agree with Alex, at runtime, zod is a must

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