Javascript过滤器但返回键而不是值

Question

此函数工作正常，但我不希望它返回值，但键：

const search = [2342,1900,1800,2310]

search = search.filter(function (el) { return el > 2200; });

所以它应该返回[0,3]而不是[2342,2310]

Answer 1

您可以获取密钥，然后使用它们访问数组，并基于此进行过滤：const search = [2342,1900,1800,2310];const result = Object.keys(search)  .filter(key => search[key] > 2200)  .map(key => Number(key))  console.dir(result)或者，对于更有趣的事情：const search = [2342,1900,1800,2310];const pipe = (...fns) => x => fns.reduce((v, f) => f(v), x);const filter = f => a => a.filter(f);const map = f => a => a.map(f);const toPairs = o => Object.keys(o)  .map(k => [k, o[k]]);  const take = i => a => a[i];const gte = a => b => b >= a;const toNumber = x => Number(x);const bigEnough = gte(2200);const itemOneIsBigEnough = pipe(  take(1),  bigEnough);const getTheFirstItemAsANumber = pipe(take(0), toNumber);const doTheThing = pipe(  toPairs,  filter(    itemOneIsBigEnough  ),  map(getTheFirstItemAsANumber),);const result = doTheThing(search);console.dir(result);

Answer 2

您可以获取键并按值检查过滤。const    search = [2342, 1900, 1800, 2310],    indices = [...search.keys()].filter(i => search[i] > 2200);console.log(indices);

Answer 3

最简单的方法是只是Array#reduce项目：const search = [2342,1900,1800,2310]const result = search.reduce(function (result, el, index) {  if(el > 2200) {    result.push(index);  }  return result;}, []);console.log(result);