dynamic_form.js

// Bind it to click event of that specific button.

const buildFormFromTemplateBtn = (evt: Event,
  addBtn: HTMLAnchorElement,
  editorIdx: number,
  isNewVersion: boolean = false) => {
  
  if (evt.target instanceof window.HTMLAnchorElement) {
    // Swap in the time to generate new unique key for a form input.
    const time: number = new Date().getTime()
    const uniqueId = addBtn.getAttribute('data-id') || ''
    const regex: RegExp = new RegExp(uniqueId, 'g')
    const templateString: string = addBtn.getAttribute('data-template-for-insertion') || ''
    const uniqueTemplateString: string = templateString.replace(regex, time.toString())
    const form: HTMLDivElement = document.createElement('div')
    const htmlTemplate = stringToHtml(uniqueTemplateString)
    if (htmlTemplate) {
      form.innerHTML = htmlTemplate
      if (!isNewVersion) {
        const input: HTMLInputElement = ((form.querySelector('input[type="text"], textarea'): any): HTMLInputElement)
        if (input) {
          input.value = ''
        }
      }
      // make sure new input is empty

      const positionInput = ((form.querySelector('.position-input'): any): HTMLInputElement)
      if (positionInput) {
        // Index start from 0 so -1
        const nextPosition: ?number = countEditorContent(editorIdx) - 1
        positionInput.value = String(nextPosition)
      }
      return form.firstChild
    } else {
      throw new FormTemplateError('Cannot parsed template string from Rails: DynamicFormHelper')
    }
  }
}