Method slice

src/MagicString.ts:1101–1163

* Returns the content of the generated string that corresponds to the slice between `start` and `end` of the original string. * Throws error if the indices are for characters that were already removed.

(start: number = 0, end: number = this.original.length - this.offset)

   * Throws error if the indices are for characters that were already removed.
   */
  slice(start: number = 0, end: number = this.original.length - this.offset): string {
    start = start + this.offset
    end = end + this.offset

    if (this.original.length !== 0) {
      if (start < 0)
        start = Math.max(0, start + this.original.length)
      if (end < 0)
        end = Math.max(0, end + this.original.length)
    }

    let result = ''

    // find start chunk
    let chunk = this.firstChunk
    while (chunk && (chunk.start > start || chunk.end <= start)) {
      // found end chunk before start
      if ((chunk.start < end && chunk.end >= end) || (end === 0 && chunk.start === 0)) {
        return result
      }

      chunk = chunk.next
    }

    if (chunk && chunk.edited && chunk.start !== start) {
      throw new MagicStringError(`cannot use edited character ${start} as slice start anchor`)
    }

    const startChunk = chunk
    while (chunk) {
      // for end === 0 the slice ends at the very start of the original, so stop
      // once the walk reaches the chunk holding that position, taking nothing from it
      if (end === 0 && chunk.start === 0) {
        break
      }

      if (chunk.intro && (startChunk !== chunk || chunk.start === start)) {
        result += chunk.intro
      }

      const containsEnd = chunk.start < end && chunk.end >= end
      if (containsEnd && chunk.edited && chunk.end !== end) {
        throw new MagicStringError(`cannot use edited character ${end} as slice end anchor`)
      }

      const sliceStart = startChunk === chunk ? start - chunk.start : 0
      const sliceEnd = containsEnd ? chunk.content.length + end - chunk.end : chunk.content.length

      result += chunk.content.slice(sliceStart, sliceEnd)

      if (chunk.outro && (!containsEnd || chunk.end === end)) {
        result += chunk.outro
      }

      if (containsEnd) {
        break
      }