Function executeJoin

source code/vim/operators.ts:260–291

(count: number, ctx: OperatorContext)

 * Execute join lines (J command).
 */
export function executeJoin(count: number, ctx: OperatorContext): void {
  const text = ctx.text
  const lines = text.split('\n')
  const { line: currentLine } = ctx.cursor.getPosition()

  if (currentLine >= lines.length - 1) return

  const linesToJoin = Math.min(count, lines.length - currentLine - 1)
  let joinedLine = lines[currentLine]!
  const cursorPos = joinedLine.length

  for (let i = 1; i <= linesToJoin; i++) {
    const nextLine = (lines[currentLine + i] ?? '').trimStart()
    if (nextLine.length > 0) {
      if (!joinedLine.endsWith(' ') && joinedLine.length > 0) {
        joinedLine += ' '
      }
      joinedLine += nextLine
    }
  }

  const newLines = [
    ...lines.slice(0, currentLine),
    joinedLine,
    ...lines.slice(currentLine + linesToJoin + 1),
  ]

  const newText = newLines.join('\n')
  ctx.setText(newText)
  ctx.setOffset(getLineStartOffset(newLines, currentLine) + cursorPos)
  ctx.recordChange({ type: 'join', count })
}

/**
 * Execute paste (p/P command).