目前我有一个数组级别包含其他名为level的数组,这些数组包含阶段.
我想用一个名为position的新属性映射一个级别内的所有对象.该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,-1,1,2,3,4 …
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
}
解决方法
你可以用两个嵌套的地图做到这一点：
const distanceLevels = [
[{
"id": 1
},[{
"id": 6
}]
]
const mappedLevels = distanceLevels.map(level =>
level.map((stage,index,lvl) => (
{...stage,position: index - (lvl.length - 1) / 2}
))
);
console.log(mappedLevels);