将数组拆分为从负到正的范围

Question

目前我有一个levels包含其他数组的数组level,这些数组包含stages.

我想用一个名为的新属性映射一个级别内的所有对象position.此位置返回距阵列中心的距离.按中心我的意思是长度/ 2.

如果数组长度是偶数,我想要以下范围

...... -3.5,-2.5,-1.5,-0.5,0.5,1.5,2.5,3.5 ......

如果数组长度不均匀,我想要以下范围

...... -4,-3,-2,-1,0,1,2,3,4 ......

我开始创造这个

const distanceLevels = [
  [{
    "id": 1
  }, {
    "id": 8
  }],
  [{
    "id": 2
  }],
  [{
    "id": 3
  }, {
    "id": 4
  }, {
    "id": 5
  }, {
    "id": 7
  }],
  [{
    "id": 6
  }]
];

function getViewLevels() {
  const viewLevels = []; // the new array as the result

  distanceLevels.forEach(level => { // one level containing the stages
    const levelLength = level.length;
    const halfLevelLength = levelLength * 0.5;
    const levelLengthIsEven = levelLength % 2 == 0;

    let viewLevel = []; // the mapped level

    if (levelLengthIsEven) {
      addViewStage(viewLevel, level[Math.floor(halfLevelLength)], 0);
    }

    for (let i = 0; i < halfLevelLength; i++) {
      let rightPosition = i - halfLevelLength;
      let leftPosition = i;
      let leftStageIndex = i;

      if (levelLengthIsEven) {
        leftPosition++;
        leftStageIndex += Math.floor(halfLevelLength) + 1;
      } else {
        rightPosition += 0.5;
        leftPosition += 0.5;
        leftStageIndex += halfLevelLength;
      }

      addViewStage(viewLevel, level[i], rightPosition);
      addViewStage(viewLevel, level[leftStageIndex], leftPosition);
    }

    viewLevel = viewLevel.sort((a, b) => a.position > b.position); // sort the result by their position, means from negative to positive
    viewLevels.push(viewLevel); // add this new view level
  });

  console.log(viewLevels); // <---- result here!
}

function addViewStage(viewLevel, stage, position) { // push a new element to the array
  viewLevel.push({
    stage: stage,
    position: position
  });
}

getViewLevels();

这是我得到的结果

我真的很挣数学.我想做的就是从中映射每个对象

阶段(对象)

至

{
   stage: stage,
   position: position // with the correct range
}

Answer 1

你可以用两个嵌套来做到这一点maps:

const distanceLevels = [
  [{
    "id": 1
  }, {
    "id": 8
  }],
  [{
    "id": 2
  }],
  [{
    "id": 3
  }, {
    "id": 4
  }, {
    "id": 5
  }, {
    "id": 7
  }],
  [{
    "id": 6
  }]
]

const mappedLevels = distanceLevels.map(level =>
  level.map((stage, index, lvl) => (
    {...stage, position: index - (lvl.length - 1) / 2}
  ))
);

console.log(mappedLevels);