数组项前移后移（用于排序）

[54leibo]

/**
 * @arr: {Array} 操作数组
 * @startPos: {Number} 需要移动数据开始项
 * @length: {Number} 需要移动数据项数
 * @moveSteps: {Number} 需要移动位数, positive number move right, minus number move left
 * @return {Array}
 * */
      const moveArrayItem = (arr, startPos, length, moveSteps) => {
        if (!(arr instanceof Array)) {
          throw new Error(`arr can only be: Array, got:${Object.prototype.toString.call(arr)}`)
        }
        if (typeof startPos !== 'number') {
          if (startPos < 0) {
            throw new Error(`startPos can only be: positive integer, got:${startPos}`)
          }
          if (startPos.toString().indexOf('.') !== -1) {
            throw new Error(`startPos can only be: positive integer, got:${startPos}`)
          }

          throw new Error(`startPos can only be: Number, got:${startPos}`)
        }
        if (typeof length !== 'number') {
          if (length < 0) {
            throw new Error(`length can only be: positive integer, got:${length}`)
          }
          if (length.toString().indexOf('.') !== -1) {
            throw new Error(`startPos can only be: positive integer, got:${length}`)
          }

          throw new Error(`length can only be: Number, got:${length}`)
        }
        if (typeof moveSteps !== 'number') {
          throw new Error(`moveSteps can only be: Number, got:${length}`)
        }
        const originArrLen = arr.length
        const moveItems = arr.splice(startPos, length) || []

        if (moveSteps < 0) {
          moveSteps = Math.abs(moveSteps)
          arr.splice(startPos - moveSteps >= 0 ? startPos - moveSteps : 0, 0, ...moveItems)
        } else {
          arr.splice(startPos + moveSteps <= originArrLen - 1 ? startPos + moveSteps : originArrLen - 1, 0, ...moveItems)
        }

        return arr
      }

     // example
      const arr = [1, 2, 3, 4, 5, 6, 7]
      console.log(`move: ${arr}`, moveArrayItem(arr, 1, 2, 1)) // [1, 4, 2, 3, 5, 6, 7]