als-require/lib/get-fn.js

A utility for using CommonJS require in the browser and creating bundles.

const parseError = require('./parse-error')
function getFn(obj, options={}) {
   const { scriptBefore='', scriptAfter='', parameters=[] } = options

   function buildFn(fnBody,path) {
      return /*js*/`modules['${path}'] = function ____(){
   const module = { exports: {} }
   const exports = module.exports
   ${fnBody}
   return module.exports;
};`
   }
   const before = [
      parseError.toString(), 
      /*js*/`function require(path) {
         if(typeof modules[path] === 'function' && modules[path].name === '____') modules[path] = modules[path]()
         return modules[path] || null
      };`,
      scriptBefore,
   ].join('\n')
   const modulesLines = {};
   let curLastLine = 3+before.split('\n').length;
   let lastModule 
   const fns = obj.keys.map((path, i) => {
      let code = buildFn(obj.contents[path],path)
      if (i === obj.keys.length - 1) lastModule = path
      modulesLines[path] = { from: curLastLine + 1 }
      curLastLine += code.split('\n').length
      modulesLines[path].to = curLastLine
      return code
   }).join('\n')

   const body = [
      before,
      'try {',
      fns,
      `let result = modules['${lastModule}']()`,
      scriptAfter,
      `return result`,
      `} catch (error) { parseError(error, modulesLines, curLastLine) }`,
   ].join('\n')
   parameters.push('modules={}',`curLastLine = ${curLastLine}`,`modulesLines = ${JSON.stringify(modulesLines)}`)

   const fn = new Function(parameters.join(','), body)
   return fn
}

module.exports = getFn