Generate JS class file from Object

Question

I am working on a js tool which will generate Js class file (myclass.js) from an object, for example:

myObj = { width: 0,
  height: 0,
  getWidth: [Function],
  getHeight: [Function] }

I want to generate a js file myClass.js that contains the class:

 class MyClass {

   constructor (width, height) {
    this.width = width;
    this.height = height;
  } 
  getWidth () { return this.width ; }
 getHeight () { return this.height; }

}

I think about myObj.construct.toString() that return all code of class, but it works just when "myObj" is an instance of the class, in my case "MyObj" will generated dynamically.

Answer 1

You have to traverse all keys of myObj and generate + concatenate the code yourself based on each value present there. A rough spaghetti-written implementation would look like:

function objectToClassString(obj = {}, className = 'MyClass') {

  const opener = `class ${className} {`
  const closer = '}'
  const indent = (str: string) => str.replace(/^(.*)/gm, '  $1')

  const ctorArgs = [] // array of `{ argName }` objects
  const getterMethods = [] // array of `{ methodName, property }` objects

  for (const key in obj) {
    const value = obj[key]
    if (Array.isArray(value) && value[0] === Function) {
      getterMethods.push({ methodName: key, property: key.replace(/^get(.)/, (_, letter) => letter.toLowerCase()) })
    } else {
      ctorArgs.push({ argName: key })
    }
  }

  const ctorOpener = `constructor(${ctorArgs.map(data => data.argName).join(', ')}) {`
  const ctorContent = ctorArgs.map(data => `this.${data.argName} = ${data.argName};`).join('\n')
  const ctorCloser = '}'
  const ctor = [ctorOpener, indent(ctorContent), ctorCloser].join('\n')

  const methods = getterMethods
    .map(data => `${data.methodName}() { return this.${data.property}; }`)
    .join('\n')

  const classContent = [
    opener,
    indent(ctor),
    indent(methods),
    closer
  ].join('\n')

  return classContent

}

Usage:

const code = objectToClassString({
  width: 0,
  height: 0,
  getWidth: [Function],
  getHeight: [Function]
})

console.log(code)

Output:

class MyClass {
  constructor(width, height) {
    this.width = width;
    this.height = height;
  }
  getWidth() { return this.width; }
  getHeight() { return this.height; }
}