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Anatomy of a Design

A JSCAD design (script) must have at least one function defined, the main() function, which must to return a shape.

const { sphere } = require('@jscad/modeling').primitives
const main = () => {
  return sphere() // a single shape
module.exports = { main }

Or an array of shapes.

const { cube, cylinder, sphere } = require('@jscad/modeling').primitives
const main () => {
  const a = cube()
  const b = sphere()
  const c = cylinder()
  return [a,b,c] // an array of shapes
module.exports = { main }

In addition, functions can be created to split the design into managable pieces, i.e. parts, etc.

const { cube, sphere } = require('@jscad/modeling').primitives
const partA = (options) => { // called from main() below
  var shapes = []
  shapes.push( sphere() )
  shapes.push( cube(options) )
  return shapes
const main = () => {
  let list = partA({radius: 10})
  return list
module.exports = { main }


As designs grow in complexity, the need for smaller, reusable parts becomes apparent. This is the time to consider using a “project”.

Projects are simple directories, containing several files (parts) of the design. For example, a project for a RC car design would have various parts. And the reusable parts can be separated out.

  • …/rc-car
    • chassis.js
    • body.js
    • tire.js
    • index.js

The 'index' within the project is the entry point of the project. The main function of the 'index' creates each of the pieces, move the pieces into position, and returns the complete design. And by convention, exports the main function.

const chassis = require('./chassis')
const body = require('./body')
const tire = require('./tire')
const main = (params) => {
  const partA = chassis(params)
  const partB = body(params)
  const tires = [
  return [partA, partB, tires]
module.exports = { main }

Design Parameters

A design can have interactive parameters by declaring a special function; getParameterDefinitions().

In applications and browsers, these parameters are presented to users, allowing users to change designs.


This function must return an array of parameter definitions, as show below.

const getParameterDefinitions = () => {
    return [
        { name: 'length', type: 'int', initial: 150, caption: 'Length?' }, 
        { name: 'width', type: 'int', initial: 100, caption: 'Width?' },

The parameters are evaluated and values are passed into the main function. Be sure to declare the main function properly.

const main = (params) => {
  var l = params.length
  var w = params.width

Parameter Types

The parameters are defined as input fields on a single HTML5 form, i.e. the list of parameters. For more information on HTML5 input fields, see some examples at W3 Schools.

Note: Browsers are NOT the same and will treat unsupported parameter types as TEXT.

Type Example Returned Value
checkbox {name: 'bigorsmall', type: 'checkbox', checked: true, caption: 'Big?'} if checked true, else false
checkbox {name: 'bigorsmall', type: 'checkbox', checked: true, initial: 20, caption: 'Big?'} if checked 20, else false
color { name: 'color', type: 'color', initial: '#FFB431', caption: 'Color?' } “#rrggbb”, use html2rgb() to convert
date {name: 'birthday', type: 'date', caption: 'Birthday?'} “YYYY-MM-DD”
email {name: 'address', type: 'email', caption: 'Email Address?'} string value
float {name: 'angle', type: 'number', initial: 2.5, step: 0.5, caption: 'Angle?'} float value
int {name: 'age', type: 'int', initial: 20, caption: 'Age?'} integer value
number {name: 'angle', type: 'number', initial: 2.5, step: 0.5, caption: 'Angle?'} float value
password {name: 'password', type: 'password', caption: 'Secret?'} string value
slider {name: 'count', type: 'slider', min: 2, max: 10, caption: 'How many?'} float value
text {name: 'name', type: 'text', caption: 'Name?'} string value
url {name: 'webpage', type: 'url', caption: 'Web page URL?'} string value
group { name: 'balloon', type: 'group', caption: 'Balloons' } none, only displayed

The parameters accept additional restrictions and assistance. These include 'initial', 'max', 'maxLength', 'min', 'pattern', 'placeholder', 'size', and 'step'.

There is one more special parameter type called 'choice', which defines a list of choices for selection.

const getParameterDefinitions = () => {
  return [
    { name: 'rounded', type: 'choice', caption: 'Rounded edges', values: [0, 1], captions: ['No', 'Yes (slow!)'], initial: 0 }

The list of captions are those shown as a pull down list. The list of values define a value for each caption. And, the chosen value is passed into the main function.